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How to digitally sign an existing PDF document using C# and VB.NET

Platform: WinForms |
Control: PDF

Syncfusion Essential PDF is a .NET PDF library used to create, read, and edit PDF documents. Using this library, you can digitally sign an existing PDF document using C# and VB.NET.

 Steps to digitally sign an existing PDF document programmatically:

  1. Create a new C# console application project. Create a console application project
  2. Install the Syncfusion.Pdf.WinForms NuGet package as reference to your .NET Framework application from NuGet.org. NuGet reference screenshot
  3. Include the following namespaces in Program.cs file.


using Syncfusion.Pdf;
using Syncfusion.Pdf.Graphics;
using Syncfusion.Pdf.Parsing;
using Syncfusion.Pdf.Security;



Imports Syncfusion.Pdf
Imports Syncfusion.Pdf.Graphics
Imports Syncfusion.Pdf.Parsing
Imports Syncfusion.Pdf.Security


  1. Use the following code snippet to digitally sign an existing PDF document.


//Loads a PDF document
PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf");
//Gets the first page of the document
PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;
//Gets the first signature field of the PDF document
PdfLoadedSignatureField field = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;
//Creates a certificate
PdfCertificate certificate = new PdfCertificate(@"PDF.pfx", "syncfusion");
//Add signature
field.Signature = new PdfSignature(loadedDocument, page, certificate, "Signature", field);
field.Signature.ContactInfo = "johndoe@owned.us";
field.Signature.LocationInfo = "Honolulu, Hawaii";
field.Signature.Reason = "I am author of this document.";
//Draw image to signature appearance
PdfBitmap image = new PdfBitmap("signature.jpg");
field.Signature.Appearance.Normal.Graphics.DrawImage(image, 0, 0, field.Bounds.Width, field.Bounds.Height);
//Saves the document
//Closes the document
//This will open the PDF file so, the result will be seen in default PDF viewer 



'Loads a PDF document
Dim loadedDocument As New PdfLoadedDocument("Input.pdf")
'Gets the first page of the document
Dim page As PdfLoadedPage = TryCast(loadedDocument.Pages(0), PdfLoadedPage)
'Gets the first signature field of the PDF document
Dim field As PdfLoadedSignatureField = TryCast(loadedDocument.Form.Fields(0), PdfLoadedSignatureField)
'Creates a certificate
Dim certificate As New PdfCertificate("PDF.pfx", "syncfusion")
'Add signature
field.Signature = New PdfSignature(loadedDocument, page, certificate, "Signature", field)
field.Signature.ContactInfo = "johndoe@owned.us"
field.Signature.LocationInfo = "Honolulu, Hawaii"
field.Signature.Reason = "I am author of this document."
'Draw image to signature appearance
Dim image As New PdfBitmap("signature.jpg")
field.Signature.Appearance.Normal.Graphics.DrawImage(image, 0, 0, field.Bounds.Width, field.Bounds.Height)
'Saves the document
'Closes the document
'This will open the PDF file so, the result will be seen in default PDF viewer 


A complete working sample can be downloaded from DigitalSignatureSample.zip.

By executing the program, you will get the PDF document as follows. Output document screenshot

Take a moment to peruse the documentation, where you can find options like adding a digital signature using stream, adding a timestamp in digital signature and features like redacting PDF document and protect PDF document with code examples.

Refer here to learn more about PDF digital signature and timestamp in Essential PDF.


Starting with v16.2.0.x, if you reference Syncfusion assemblies from trial setup or from the NuGet feed, include a license key in your projects. Refer to link to learn about generating and registering Syncfusion license key in your application to use the components without trail message.


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You must log in to leave a comment
Navneet Saraswat
Nov 27, 2017


the sample download link Signature_753104ff.zip is not working, can you please check?



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