PDF document security and digital signing via C #

This is preety old post. But still relevant. PDFsharp (PdfSharp) has significant limitations when it comes to PDF security and digital signatures:

PDFsharp Limitations

1. No built-in support for encryption/security settings - PDFsharp cannot set permissions like "Content Copying Not Allowed" or "Page Extraction Not Allowed"
2. No digital signature support - PDFsharp cannot digitally sign PDF documents
    

   Syncfusion offers comprehensive PDF security and signing features.

   Install: 
    

   Example:
    

   using Syncfusion.Pdf;
   using Syncfusion.Pdf.Security;
   using Syncfusion.Pdf.Graphics;
   
   public void SecureAndSignWithSyncfusion(string inputPath, string outputPath)
   {
       // Load existing PDF
       using var document = new PdfLoadedDocument(inputPath);
       
       // Set security
       document.Security = new PdfSecurity();
       document.Security.OwnerPassword = "ownerPassword";
       document.Security.Permissions = PdfPermissionsFlags.Print | 
                                      PdfPermissionsFlags.Accessible | 
                                      PdfPermissionsFlags.DocumentAssembly;
       // This automatically restricts copying, editing, etc.
       
       // Save with security
       document.Save(outputPath);
       document.Close();
       
       // Note: Digital signing requires additional Syncfusion licensing
   }

    

To protect your document from various security risks and ensure it remains tamper-proof, you should digitally sign the PDF. A digital signature adds authenticity, integrity, and protection to your file. If you also need a certificate for signing, you can get a Code Signing Certificate from SignMyCode.com.

You can use Spire.PDF for .NET library to digitally sign a PDF and set the security permissions at once.