add digital signature to PDF C#

In this guide, we will show you how to add a digital signature to a PDF file in C#, including the necessary code and steps to get started. Whether you are a developer or a user, this guide will provide you with the information you need to add a digital signature to a PDF document in C#. Also, we will demonstrate how to verify a digitally signed PDF file programmatically in C#.

C# Library for Digital Signatures in PDF

To add and verify digital signatures in PDF, we’ll use Aspose.PDF for .NET. It is a powerful PDF manipulation library for creating, editing, converting, and digitally signing PDF documents. Not only this, you can get a free license to sign your PDF files without any limitations.

You can download Aspose.PDF for .NET or install it using NuGet.

PM> Install-Package Aspose.PDF

How to Add Digital Signature to PDF in C#

The following are the steps to add a digital signature to a PDF in C#.

  • Create an object of the Document class and initialize it with the PDF document’s path.
  • Create an object of PdfFileSignature class and initialize it with the Document class’s object.
  • Create an object of PKCS7 class and initialize it with a certificate path and password.
  • Create and initialize the object of DocMDPSignature class for the MDP signature type.
  • Create a Rectangle for signature placement.
  • Digitally sign PDF document using PdfFileSignature.Certify() method.
  • Save the document using PdfFileSignature.Save() method.

C# Code for Adding Digital Signature to PDF

The following code sample shows how to add a digital signature to a PDF in C#.

C# Digitally Sign PDF with Timestamp Server

You can also add a digital signature to a PDF document with the TimeStamp server by providing its details using the TimestampSettings class.

The following code sample shows how to digitally sign a PDF document with a TimeStamp server in C#.

Verify Digitally Signed PDF in C#

The following are the steps to verify the digital signature in a PDF document:

  • Create an object of the Document class and initialize it with the PDF document’s path.
  • Create an object of PdfFileSignature class and initialize it with the Document class’s object.
  • Access all the signatures of the PDF document.
  • Verify the validity of the signature using PdfFileSignature.VerifySigned() method.

The following code sample shows how to verify the digital signature in PDF using C#.

Free PDF Digital Signature Library

You can get a free temporary license and add digital signatures to PDF files without any limitations.

Conclusion

In this article, you have learned how to add digital signatures to PDF files in C#.NET. Furthermore, you have seen how to verify the digitally signed PDF files programmatically in C#. You can simply install Aspose.PDF for .NET in your applications and digitally sign your PDF files seamlessly.