PDF digital signature usig PointCasttle

[Marcio]

Hi

I need to digitally sign (RSA and ECDSA) a PDF document using the PointCastle Library(https://pub.dev/packages/pointycastle).

Can anybody help me? Any sample code?

Thanks in advance

[Surya Venkatesan]

Hi Marcio,

As of now, We do not have support for signing PDF document by using PointCastle Library(https://pub.dev/packages/pointycastle). Currently, we are analyzing on this and we will update the further details on February 22^nd 2022.

Refer to the following article to get more for signing a PDF document,

https://help.syncfusion.com/flutter/pdf/working-with-digital-signature

Regards,

Surya V

[Marcio]

Surya

Thanks for your prompt response. As I could understand in the code sample for digital signature, you use PointCastle n the X.509 package. Am I correct ? 

Thanks again

Regards

[Surya Venkatesan]

Hi Marcio,

No, We are not using PointyCastle for our digital signing process. As we said earlier, we are analyzing on this and we will update the further details on February 22^nd 2022.

Regards,

Surya V

[Surya Venkatesan]

Hi Marcio,

We won’t be able to sign the PDF document directly using the pointycastle package but it is possible to use pointycastle package to generate signed bytes and externally sign the PDF document using the signature data.

Kindly use the following link for externally signing the PDF document, https://help.syncfusion.com/flutter/pdf/working-with-digital-signature#externally-sign-a-pdf-document

Kindly use the following code snippet for add signed data to PDF,

//Class for singing a PDF document externally.

class PdfExternalSigner implements IPdfExternalSigner {

  //Hash algorithm.

  @override

  DigestAlgorithm get hashAlgorithm => DigestAlgorithm.sha256;

 

  //Sign message digest.

  @override

  SignerResult sign(List<int> message) {

    final privateKey = _ InitializeRSAPrivateKey();

    var signer = RSASigner(SHA256Digest(), '0609608648016503040201');

    signer.init(true, PrivateKeyParameter<RSAPrivateKey>(privateKey));

    List<int> signedBytes =

        signer.generateSignature(Uint8List.fromList(message)).bytes;

    return SignerResult(signedBytes);

  }

}

 

PrivateKey InitializeRSAPrivateKey() {

  var rsapars = RSAKeyGeneratorParameters(BigInt.from(65537), 2048, 5);

  var secureRandom = FortunaRandom();

  var random = Random.secure();

  var seeds = <int>[];

  for (var i = 0; i < 32; i++) {

    seeds.add(random.nextInt(255));

  }

  secureRandom.seed(KeyParameter(Uint8List.fromList(seeds)));

  var params = ParametersWithRandom(rsapars, secureRandom);

  var keyGenerator = RSAKeyGenerator();

  keyGenerator.init(params);

  return keyGenerator.generateKeyPair().privateKey;

}

Regards,

Surya V

[Marcio]

Thanks, Surya

Can you please send an example using the above code? The document that you indicate uses a PFX file with a certificate and I don't have this file and I don't want to create this file? 

Regards

[Surya Venkatesan]

Hi Marcio,

In Syncfusion Flutter PDF library, we won’t be able to externally sign a PDF document without valid certificate data. We have also attached a simple sample for externally signing PDF using some generated signed bytes from pointycastle package.

Kindly use the following package to download the sample, https://www.syncfusion.com/downloads/support/directtrac/general/ze/flutter_sample-517615916

Regards,

Surya V

[Marcio]

Hi Surya V

Thanks for your reply. I am sorry for the delay but I was busy testing our solution .

Although I managed to sign the PDF Form using our PointCastle as directed by your post The signature file is not shown in the form. Everything works fine, no error, but the field is not shown.

Then I tested your code and it has the same behaviour.

Any Clue!

Best regards

[Surya Venkatesan]

Hi Marcio,

We recommend you enable the default set appearance of the form fields. Because few cases Form fields may appear empty in an adobe reader due to the absence of the appearance dictionary. To resolve this, you need to enable the Adobe Reader default appearance by using the setDefaultAppearance method in PdfForm class. Refer to the following UG documentation for more details, https://help.syncfusion.com/flutter/pdf/working-with-forms#troubleshooting and kindly try with the following code snippet and let us know the result,

document.form.setDefaultAppearance(true);

Regards,

Surya V

[Marcio]

Hi  Surya

I inserted the code you suggested and I can see that there is a signature in the document. But no matter where a position the signature field it appears in the same location. Also when I show with the SfPdfViewer ​the signature des not appear at all!

myCripto = Cripto();

await myCripto!.fromSecureStorage();

final PdfSignatureField signatureField = await PdfSignatureField(

page, 'Signature',

bounds: Rect.fromLTWH(-65, 50, 200, 100));

final PdfSignature sign = await PdfSignature(

cryptographicStandard: CryptographicStandard.cades,

digestAlgorithm: DigestAlgorithm.sha256);

var extSigner = await PdfExternalSigner();

extSigner.myCripto = myCripto;

final IPdfExternalSigner externalSignature = extSigner;

sign.addExternalSigner(externalSignature,

<List<int>>[base64.decode(this.myCripto!.certbase64!)]);

signatureField.signature = await sign;

await document.form.fields.add(signatureField);

Here is the link to the file. https://drive.google.com/file/d/1Iz6JPGfnycdv8896WjJ89hDhQABctC_1/view?usp=sharing

Any ideia ? Thanks! Best regards!

[Surya Venkatesan]

Hi Marcio,

At present, our Flutter PDF Viewer doesn’t have support for digital signature. We have a workaround to viewing the existing digital signature in the PDF document, kindly refer to the following link,

https://www.syncfusion.com/downloads/support/directtrac/general/ze/annnotation-578168701.zip

We have logged a feature request for this support in the PDF document library. We do not have any immediate plans to implement these features and we will implement this support in any of our upcoming releases. We usually have an interval of at least three months between releases, at the planning stage for every release cycle, we review all open features. We will let you know when this feature is implemented.

Please find the feedback link to track the implementation of the feature below,

https://www.syncfusion.com/feedback/26234/support-for-digital-signature

Kindly refer to the below link for more information about preserving the existing annotation in Syncfusion Flutter PDFViewer

https://www.syncfusion.com/kb/13014/how-to-preserve-the-existing-annotation-in-flutter-pdf-viewer-sfpdfviewer

Regards,

Surya V

[Marcio]

Hi Surya

Thanks for your replay.

The code didn't work for the digital signature in the PDF Viewer. 

However, I can see, in Adobe Pdf Reader, that the signature is in the document but I can position the signature in the right place and the size of the signature shown in the document is truncated whatever the parameters I use in Rect.LTWH.

myCripto = Cripto();

await myCripto!.fromSecureStorage();

final PdfSignatureField signatureField = await PdfSignatureField(

page, 'Signature',

bounds: Rect.fromLTWH(-65, 50, 200, 100));

final PdfSignature sign = await PdfSignature(

cryptographicStandard: CryptographicStandard.cades,

digestAlgorithm: DigestAlgorithm.sha256);

var extSigner = await PdfExternalSigner();

extSigner.myCripto = myCripto;

final IPdfExternalSigner externalSignature = extSigner;

sign.addExternalSigner(externalSignature,

<List<int>>[base64.decode(this.myCripto!.certbase64!)]);

signatureField.signature = await sign;

await document.form.fields.add(signatureField);

Here is the link to the file. https://drive.google.com/file/d/1Iz6JPGfnycdv8896WjJ89hDhQABctC_1/view?usp=sharing

Any idea? Thanks! Best regards!

[Surya Venkatesan]

Hi Marcio,

The code didn't work for the digital signature in the PDF Viewer.

Currently, We are analyzing on the requested sample and will update the further details on March 28, 2022.

However, I can see, in Adobe Pdf Reader, that the signature is in the document but I can position the signature in the right place and the size of the signature shown in the document is truncated whatever the parameters I use in Rect.LTWH.   myCripto = Cripto();     await myCripto!.fromSecureStorage();     final PdfSignatureField signatureField = await PdfSignatureField(         page, 'Signature',         bounds: Rect.fromLTWH(-65, 50, 200, 100));

We have checked the provided code snippet containing -65 in the left position(x-axis of page position). We recommend you use the positive values in the bounds(if the page and its graphics are in zero degrees) to get a better result. Eg: bounds: Rect.fromLTWH(65, 50, 200, 100));

Regards,

Surya V

[Marcio]

Hi Surya, Thanks for your attention!

your suggestion :

"We have checked the provided code snippet containing -65 in the left position(x-axis of page position). We recommend you use the positive values in the bounds(if the page and its graphics are in zero degrees) to get a better result.

Eg: bounds: Rect.fromLTWH(65, 50, 200, 100));"

Does not work! The signature always appears at the same position no matter a change the Rect.fromLTWH's parameters. This seems to have no affect on the final PDF document.

Below some of the relevant code. Sorry I couldn't post the whole file. 

Btw, all other elements appears on the right position.

Best regards

SignerResult sign(List<int> message) {

var eccsassinatura;

if (myCripto != null) {

eccsassinatura = myCripto!.ECSign(Uint8List.fromList(message));

;

} else

throw ("Cripto nao inicializada");

return SignerResult(eccsassinatura);

}

}

class Pdfclass {

// constructor

Cripto? myCripto;

PdfPage? page;

PdfDocument document = PdfDocument();

firebase_storage.FirebaseStorage storage =

firebase_storage.FirebaseStorage.instance;

Pdf() {} //Set the font

// cria PDF do aviso de Saida

Future<void> createAvisodeSaida(

AvisoSaida avisoSaida, String filename, String waterMark) async {

try {

//Set the page size

document.pageSettings.size = PdfPageSize.a4;

//Draw text

page = document.pages.add();

var imageBuffer = await rootBundle.load('imagens/Avisodesaida.jpg');

var byteData = imageBuffer.buffer

.asUint8List(imageBuffer.offsetInBytes, imageBuffer.lengthInBytes);

// var imageBuffer = File('../imagens/Avisodesaida.jpg').readAsBytesSync();

//Draw the image

page!.graphics.drawImage(

PdfBitmap(byteData),

Rect.fromLTWH(

0, 0, page!.getClientSize().width, page!.getClientSize().height));

// Draw Nome da Marina

page!.graphics.drawString(avisoSaida.nomeMarinaIate!,

PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(223, 136, 100, 100));

// Draw Data

page!.graphics.drawString(

avisoSaida.data!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(122, 200, 100, 100));

// Draw Nome do Comandante

page!.graphics.drawString(avisoSaida.nomeComandante!,

PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(117, 220, 400, 100));

// Draw Nome da Embarcacao

page!.graphics.drawString(avisoSaida.nomeEmbarcacao!,

PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(211, 246, 100, 100));

// Draw Nome Tipo

page!.graphics.drawString(

avisoSaida.tipo!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(375, 246, 100, 100));

// Draw Destino

page!.graphics.drawString(

avisoSaida.destino!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(201, 268, 100, 100));

// Draw Previsao de Saida

page!.graphics.drawString(avisoSaida.previsaoSaida!,

PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(205, 292, 100, 100));

// Draw Datade Chegada

page!.graphics.drawString(avisoSaida.previsaoChegada!,

PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(400, 292, 100, 100));

// Draw Numero de Pessoas

page!.graphics.drawString(avisoSaida.numeroPessoas!.toString(),

PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(261, 314, 100, 100));

// Draw Observacoes

page!.graphics.drawString(

avisoSaida.observacoes!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(150, 336, 300, 100));

// Draw Watermark

if (waterMark != "") {

page!.graphics.setTransparency(0.20);

page!.graphics.rotateTransform(-40.0);

page!.graphics.drawString(

waterMark, PdfStandardFont(PdfFontFamily.helvetica, 50),

pen: PdfPens.red,

brush: PdfBrushes.red,

bounds: Rect.fromLTWH(100, 450, page!.getClientSize().width,

page!.getClientSize().height));

}

//Assina e salva documento

await _signPDF();

document.form.setDefaultAppearance(true);

_getAnnotations();

pdfbytes = await document.save();

document.dispose();

//Get external storage directory

Directory directory = (await getApplicationDocumentsDirectory());

//Get directory path

String path = directory.path;

//Create an empty file to write PDF data

var ts = DateFormat('dd-MM-yyyy:HH:mm:ss:ms').format(DateTime.now());

File file = File('$path/avisodesaida1' + ts + '.pdf');

//Write PDF data

await file.writeAsBytes(pdfbytes!, flush: true);

//Open the PDF document in mobile

await OpenFile.open('$path/avisodesaida1' + ts + '.pdf');

;

} catch (exception) {

print("Erro = " + exception.toString());

}

}

Future<void> _signPDF() async {

PdfGraphics graphics = page!.graphics;

myCripto = Cripto();

if (!await myCripto!.fromSecureStorage()) return;

//Sets an image for signature field

var imageBuffer = await rootBundle.load("imagens/navegacaoNovoLogo.png");

var imageBytes = imageBuffer.buffer

.asUint8List(imageBuffer.offsetInBytes, imageBuffer.lengthInBytes);

PdfBitmap signatureImage = new PdfBitmap(imageBytes);

final PdfSignatureField signatureField = await PdfSignatureField(

page!, 'Signature',

bounds: Rect.fromLTWH(200, 550, 200, 200));

final PdfSignature sign = await PdfSignature(

cryptographicStandard: CryptographicStandard.cades,

digestAlgorithm: DigestAlgorithm.sha256,

signedName: "Marcio",

contactInfo: "[email protected]",

reason: "Aviso de Saida",

locationInfo: "rio de janeiro");

var extSigner = await PdfExternalSigner();

//Draws the signature image

extSigner.myCripto = myCripto;

final IPdfExternalSigner externalSignature = extSigner;

sign.addExternalSigner(externalSignature,

<List<int>>[base64.decode(this.myCripto!.certbase64!)]);

signatureField.signature = await sign;

await document.form.fields.add(signatureField);

// graphics.drawImage(signatureImage, Rect.fromLTWH(0, 400, 50, 50));

}

[Surya Venkatesan]

Hi Marcio,

We have prepared a sample to add digital signature in a specific coordinate with help of Syncfusion PDF and SfSignaturePad package. The sample can be downloaded from the following link.

https://www.syncfusion.com/downloads/support/directtrac/general/ze/pdfviewer_signature1106623277.zip

We tried to prepare the sample with the provided document, but the signature is not added and flatten while saving the PDFDocument. We are checking on this issue and will update the further details on 30 March 2022.

Regards,

Surya V

[Marcio]

Hi Surya

Thanks for your reply!

I tried to run the sample in my computer and It didn't work. The digital signature is not shown. Only the image of the signature collected in the signature pad. I have tried many different approaches but had no success.

Best regards 

[Deepika Ravi]

Hi Marcio,

We have prepared the sample for adding signature in the existing PDF document(provided) and it can be downloaded from the following link,

https://www.syncfusion.com/downloads/support/directtrac/general/ze/pdfviewer_signature48823757-77338112.zip

We have also checked the reported issue in the workaround sample provided on 28 March, but the provided sample is working fine on our side. For your reference, we have prepared the output screen record of the sample, which can be downloaded from the following link,

https://www.syncfusion.com/downloads/support/directtrac/general/ze/Screenrecord-509618322.zip

Regards,

Deepika Ravi

[Marcio]

Hi Deepika !

Thanks for you answer !

You same works with the signature pad. It shows the image of the hand signature. However the fields of the digital signature is not shown in the actual  pdf form.

PdfSignatureField field = PdfSignatureField(page, 'signature',

bounds: const Rect.fromLTRB(300, 500, 550, 700),

signature: PdfSignature(

//Creates a certificate instance from the PFX file with a private key.

certificate: PdfCertificate(certificateBytes, 'password123'),

contactInfo: '[email protected]',

locationInfo: 'Honolulu, Hawaii',

reason: 'I am author of this document.',

digestAlgorithm: DigestAlgorithm.sha256,

cryptographicStandard: CryptographicStandard.cms));

This field is not shown! I am trying to show the parameters of the field like location info, contact info and the image linked to the field.

Any idea why?

Best regards

[Deepika Ravi]

Hi Marico,

Thank you for your update.

As mentioned earlier, SfPDFViewer doesn't provide support for digital signature. But as a workaround, we have flattened the signature and displayed it in PDFViewer. While flattening, the signature will be preserved as an image, and the signature's properties will be lost so the information like location, the contact won't be available in PDFViewer.

If the PDF document is saved without flattening, then the signature will be available in PDF form which can be viewed using an adobe pdf reader. Please find its code and screenshot.

Code Snippet:

final ByteData docBytes = await rootBundle.load("assets/aviso2.pdf");
 final Uint8List documentBytes = docBytes.buffer.asUint8List();
 ByteData certBytes = await rootBundle.load("assets/certificate.cer");
 final Uint8List certificateBytes = certBytes.buffer.asUint8List();
 PdfDocument document = PdfDocument(inputBytes: documentBytes);
 //Adds a new page.
 PdfPage page = document.pages[0];
 final ByteData privateKey = await rootBundle.load("assets/privatekey.pem");
 final Uint8List privateKeyBytes = privateKey.buffer.asUint8List();
 final PdfSignature signature = PdfSignature(
     //Creates a certificate instance from the PFX file with a private key.
     certificate: null,
     contactInfo: '[email protected]',
     locationInfo: 'Honolulu, Hawaii',
     reason: 'I am author of this document.',
     digestAlgorithm: DigestAlgorithm.sha256,
     cryptographicStandard: CryptographicStandard.cms);
 signature.addExternalSigner(
     PdfExternalSigner(privateKeyBytes), [certificateBytes]);
//Creates a digital signature and sets signature information.
 PdfSignatureField field = PdfSignatureField(page, 'signature',
     bounds: const Rect.fromLTWH(0, 0, 200, 100), signature: signature);

 //Gets the signature field appearance graphics.
 PdfGraphics? graphics = field.appearance.normal.graphics;

 final ByteData imgBytes = await rootBundle.load("assets/sign.png");
 final Uint8List imageBytes = imgBytes.buffer.asUint8List();

 //Draws the signature image.
 graphics?.drawImage(PdfBitmap(imageBytes),
     Rect.fromLTWH(0, 0, field.bounds.width, field.bounds.height));
 //Add a signature field to the form.
 document.form.fields.add(field);

 //Save the signed document.
 final signatureDocument = Uint8List.fromList(document.save());
 document.dispose();

 //load the existing document.
 PdfDocument flattenDocument = PdfDocument(inputBytes: signatureDocument);

 //Flattens the PDF form field annotation
    flattenDocument.form.flattenAllFields();
 List<int> bytes = flattenDocument.save();
 //Dispose the document
 document.dispose();
 AnchorElement(
     rel='nofollow' href:
     "data:application/octet-stream;charset=utf-16le;base64,${base64.encode(bytes)}")
   ..setAttribute("download", "output.pdf")
   ..click();

 

Output Screenshot:

https://www.syncfusion.com/downloads/support/directtrac/general/SC1580~1-1684108337.png

Regards,

Deepika Ravi

[Marcio]

Hi Deepika!

Thanks for your post! I have tried every sample you sent me and the signature is not shown. I Flatenned the fields and it shows the signature's image PDFViewer. If I don't flat the fields and try to show the document in Adobe and it also does not show the signature fields. I am stuck in on this. Below my last try:

 

Future<void> _signPDF() async {

PdfGraphics? graphics;

myCripto = Cripto();

if (!await myCripto!.fromSecureStorage()) return;

// cria o adinatura

final PdfSignature sign = await PdfSignature(

cryptographicStandard: CryptographicStandard.cades,

digestAlgorithm: DigestAlgorithm.sha256,

signedName: "Marcio",

contactInfo: "[email protected]",

reason: "Aviso de Saida",

locationInfo: "rio de janeiro");

var extSigner = await PdfExternalSigner();

//Draws the signature image

extSigner.myCripto = myCripto;

final IPdfExternalSigner externalSignature = extSigner;

sign.addExternalSigner(externalSignature,

<List<int>>[base64.decode(this.myCripto!.certbase64!)]);

// cria o Field Signature

final PdfSignatureField signatureField = await PdfSignatureField(

page!, 'Assinado Digitalmente',

bounds: const Rect.fromLTWH(100, 330, 200, 100), signature: await sign);

// carrega a imagem da assinatura

var imageBuffer = await rootBundle.load("imagens/signature.png");

var imageBytes = imageBuffer.buffer

.asUint8List(imageBuffer.offsetInBytes, imageBuffer.lengthInBytes);

PdfBitmap signatureImage = new PdfBitmap(imageBytes);

graphics = signatureField.appearance.normal.graphics;

graphics!.drawImage(signatureImage, Rect.fromLTWH(0, 0, 20, 20));

// adiciona o Filed da assinatura no documento

var result = await document.form.fields.add(signatureField);

print("Resultado = " + result.toString());

}

// Document creation

try {

//Set the page size

document.pageSettings.size = PdfPageSize.a4;

//Draw text

page = document.pages.add();

var imageBuffer = await rootBundle.load('imagens/tie.png');

var byteData = imageBuffer.buffer

.asUint8List(imageBuffer.offsetInBytes, imageBuffer.lengthInBytes);

//Draw the image

print("Width " + page!.getClientSize().width.toString());

print("Height " + page!.getClientSize().height.toString());

page!.graphics.drawImage(

PdfBitmap(byteData),

Rect.fromLTWH(

0, 0, page!.getClientSize().width, page!.getClientSize().height));

// Draw Nome

page!.graphics.drawString(

tie.holderName!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(60, 150, 500, 100));

// Draw Numero de Inscrico

page!.graphics.drawString(

tie.inscricao!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(380, 150, 500, 100));

// Draw Posto

page!.graphics.drawString(

tie.holderName!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(60, 200, 500, 100));

// Draw Data

page!.graphics.drawString(

tie.dateofEnroll!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(60, 250, 100, 500));

// Draw CPF

page!.graphics.drawString(

tie.cpf!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(180, 300, 100, 500));

// Draw Observacoes

page!.graphics.drawString(

tie.observacao!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(170, 570, 500, 100));

// Draw Local de Emissao

page!.graphics.drawString(

tie.placeOfIssuance!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(170, 610, 500, 500));

// Draw Data de Emissao

page!.graphics.drawString(

tie.dateofEnroll!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(260, 610, 400, 500));

// Draw validade

page!.graphics.drawString(

tie.expirationDate!, PdfStandardFont(PdfFontFamily.helvetica, 12),

brush: PdfBrushes.black, bounds: Rect.fromLTWH(350, 610, 100, 500));

//Assina e salva documento

await _signPDF();

document.form.setDefaultAppearance(true);

//_getAnnotations();

//Flattens the PDF form field annotation

//document.form.flattenAllFields();

pdfbytes = await document.save();

document.dispose();

//Get external storage directory

Directory directory = (await getApplicationDocumentsDirectory());

//Get directory path

String path = directory.path;

//Create an empty file to write PDF data

var ts = DateFormat('dd-MM-yyyy:HH:mm:ss:ms').format(DateTime.now());

File file = File('$path/tie1' + ts + '.pdf');

//Write PDF data

await file.writeAsBytes(pdfbytes!, flush: true);

//Open the PDF document in mobile

await OpenFile.open('$path/tie1' + ts + '.pdf');

;

} catch (exception) {

print("Erro = " + exception.toString());

}

}

[Anantha Gokula Raman Jeyaraman]

Hi Marcio,

Thank you for your patience.

As of now, only the signed document appearance will be shown on the mobile reader and the signature details will not be shown, we have confirmed this behavior by signing PDF document using Adobe and ensured that the  signature details  were not shown in the mobile. If you want to show such details like signer, location, and more, you can draw it to the signature fields appearance(as in the below screenshot). Also we have confirmed that signature appearance is preserved properly in Adobe reader with and without flattening.

Adobe viewer mobile view
Adobe viewer desktop view

Kindly use the following sample for reference, https://www.syncfusion.com/downloads/support/directtrac/general/ze/pdfviewer_signature48823757-773381121428891908

Regards,

Anantha Gokula Raman J