How to remove the digital signature from an existing PDF using C# and VB.NET
Syncfusion Essential® PDF is a .NET PDF library used to create, read, and edit the PDF documents. Using this library, you can remove the digital signature from an existing PDF using C# and VB.NET.
Steps to remove digital signature from an existing PDF programmatically:
- Create a new C# console application project.
- Install the Syncfusion.Pdf.WinForms NuGet packages as reference to your .NET Framework application from NuGet.org.
- Include the following namespaces in the Program.cs file.
C#
using Syncfusion.Pdf.Parsing;
VB.NET
Imports Syncfusion.Pdf.Parsing
- Use the following code snippet to remove digital signature from an existing PDF document.
C#
//Loads an existing PDF document
PdfLoadedDocument loadedDocument = new PdfLoadedDocument("DigitallySigned.pdf");
//Get the signature field from PdfloadedDocument form field collection
PdfLoadedSignatureField signatureField = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;
//Remove signature field from PdfLoadedDocument form field collection
loadedDocument.Form.Fields.Remove(signatureField);
//Save the document
loadedDocument.Save("DigitalSignatureRemoved.pdf");
//Close the document
loadedDocument.Close(true);
//This will open the PDF file so, the result will be seen in default PDF Viewer
Process.Start("DigitalSignatureRemoved.pdf");
VB.NET
'Loads an existing PDF document
Dim loadedDocument As New PdfLoadedDocument("DigitallySigned.pdf")
'Get the signature field from PdfloadedDocument form field collection
Dim signatureField As PdfLoadedSignatureField = TryCast(loadedDocument.Form.Fields(0), PdfLoadedSignatureField)
'Remove signature field from PdfLoadedDocument form field collection
loadedDocument.Form.Fields.Remove(signatureField)
'Save the document
loadedDocument.Save("DigitalSignatureRemoved.pdf")
'Close the document
loadedDocument.Close(True)
'This will open the PDF file so, the result will be seen in default PDF Viewer
Process.Start("DigitalSignatureRemoved.pdf")
A complete working sample can be downloaded from DigitalSignatureRemovalSample.zip
By executing the program, you will get the PDF document as follows. 
Take a moment to peruse the documentation for using digital signature in PDF, where you will find other options like support for adding digital signature to PDF, signing an existing document, and also validate the signature appearance based on signature. You can also add the signature field to a PDF document.
An online sample link demonstrates how to sign a PDF document using digital signature.
Refer here to explore the rich set of Syncfusion Essential® PDF features.
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.
