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Overview

PDF digital signature and timestamp are the best ways to protect your PDF files from being forged. Syncfusion Essential PDF is a .NET PDF library that helps you add digital signature and time stamp to your PDF files in any .NET application, whether it is on Windows Forms, WPF, ASP.NET (web forms, MVC, Core), or even UWP, Xamarin.Forms, Xamarin.Android, and Xamarin.iOS. Syncfusion provides many ways to digitally sign a document: X509 certificates, such as .pfx files with private keys and also supports hardware security modules (HSM), Online Certificate Status Protocol (OCSP), certificate revocation lists (CRL), and Windows Certificate Store for authenticity and integrity.


Customize Appearance

The Syncfusion .NET PDF library provides a completely customizable appearance for its e-signature. The content of the signature can be images, texts, graphics, and shapes.

Custom Appearance of C# pdf digital signature


C# pdf digital signature LTV

Long-Term Validation (LTV)

LTV signatures allow you to check the validity of a signature long after signing the document. All the required elements for signature validation must be embedded in the signed PDF to use LTV.


Timestamp PDF

It is possible to include the date and time of your signing the PDF as part of your certificate-based digital signature. A timestamp helps you establish when you signed the PDF and reduces the chance of an invalid signatures. Syncfusion Essential PDF makes time-stamping a PDF document possible with only a few lines of code.

Timestamp in ASP.NET digital signature PDF


Certificate details in ASP.NET digital signature PDF

Certificate Details

You can also get or retrieve the digitally signed certificate details like subject, author, and expiry date. Based on the expiry date, you can digitally sign the PDF with valid certificate again.


Additional features of digital signatures and timestamps

  • Sign existing PDFs with digital signatures.
  • Add multiple digital signatures to a PDF.
  • Add signature validation to a PDF.
  • Time-stamp an existing PDF document.
  • Time-stamp a PDF without a certificate.

PDF Digital Signature Code Example

Easily add the digital signature to a PDF document using a few simple lines of C# code as demonstrated below. Also explore our .NET PDF Example that shows how to create and modify PDF files from C# with 5 lines of code on different platforms.

PdfDocument document = new PdfDocument(); //Creates a new PDF document
PdfPageBase page = document.Pages.Add();  //Adds a new page
PdfGraphics graphics = page.Graphics;
PdfCertificate pdfCert = new PdfCertificate(@"PDF.pfx", "syncfusion");  //Creates a certificate instance from PFX file with private key
PdfSignature signature = new PdfSignature(document, page, pdfCert, "Signature");  //Creates a digital signature
PdfBitmap signatureImage = new PdfBitmap(@"signature.jpg");  //Sets an image for signature field
signature.Bounds = new RectangleF(new PointF(0, 0), signatureImage.PhysicalDimension);  //Sets signature information
signature.ContactInfo = "johndoe@owned.us";
signature.LocationInfo = "Honolulu, Hawaii";
signature.Reason = "I am author of this document.";
graphics.DrawImage(signatureImage, 0, 0);  //Draws the signature image
document.Save("Output.pdf");  //Saves and closes the document
document.Close(true);
Imports Syncfusion.Pdf

Dim document As New PdfDocument()  //Creates a new PDF document

Dim page As PdfPageBase = document.Pages.Add()  //Adds a new page

Dim graphics As PdfGraphics = page.Graphics  //Creates a certificate instance from PFX file with private key

Dim pdfCert As New PdfCertificate("PDF.pfx", "syncfusion")

Dim signature As New PdfSignature(document, page, pdfCert, "Signature")  //Creates a digital signature

Dim signatureImage As New PdfBitmap("signature.jpg")  //Sets an image for signature field

signature.Bounds = New RectangleF(New PointF(0, 0), signatureImage.PhysicalDimension)  //Sets signature info

signature.ContactInfo = "johndoe@owned.us"

signature.LocationInfo = "Honolulu, Hawaii"

signature.Reason = "I am author of this document."

graphics.DrawImage(signatureImage, 0, 0)  //Draws the signature image

document.Save("Output.pdf")  //Saves and closes the document

document.Close(True)


Awards

Greatness—it’s one thing to say you have it, but it means more when others recognize it. Syncfusion is proud to hold the following industry awards.

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