PDF: How to add invisible digital signature to a PDF document?

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Here is C#/VB.NET code that demonstrates how to add invisible digital signature to a PDF document using PdfPageDigitalSignatureHelper class:

using System.Security.Cryptography.X509Certificates;
using Vintasoft.Imaging.Pdf;

/// <summary>
/// Adds invisible digital signature to a PDF page.
/// </summary>
public class PdfPageDigitalSignatureHelper_InvisibleAppearance
{
    public static void Run()
    {
        // get the X509 certificate from .pfx-file
        using (X509Certificate2 certificate = new X509Certificate2("TestCertificate.pfx", "test"))
        {
            // create a helper that allows to add digital signature to a PDF document
            PdfPageDigitalSignatureHelper digitalSignatureHelper = new PdfPageDigitalSignatureHelper(certificate);

            // set the reason for signing
            digitalSignatureHelper.SigningReason = "Approve document";

            // add digital signature to the first PDF page, sign PDF document and save PDF document to the output file
            digitalSignatureHelper.SignDocument("TestDocumentToSign.pdf", "TestDocumentToSign-signed.pdf", 0);
        }
    }
}

VB.NET

Imports System.Security.Cryptography.X509Certificates
Imports Vintasoft.Imaging.Pdf

''' <summary>
''' Adds invisible digital signature to a PDF page.
''' </summary>
Public Class PdfPageDigitalSignatureHelper_InvisibleAppearance
    Public Shared Sub Run()
        ' get the X509 certificate from .pfx-file
        Using certificate As New X509Certificate2("TestCertificate.pfx", "test")
            ' create a helper that allows to add digital signature to a PDF document
            Dim digitalSignatureHelper As New PdfPageDigitalSignatureHelper(certificate)

            ' set the reason for signing
            digitalSignatureHelper.SigningReason = "Approve document"

            ' add digital signature to the first PDF page, sign PDF document and save PDF document to the output file
            digitalSignatureHelper.SignDocument("TestDocumentToSign.pdf", "TestDocumentToSign-signed.pdf", 0)
        End Using
    End Sub
End Class

Here is C#/VB.NET code that demonstrates how to add invisible digital signature to a PDF document using PdfPage.AddInvisibleDigitalSignature method:

using System.Security.Cryptography.X509Certificates;
using Vintasoft.Imaging.Pdf;
using Vintasoft.Imaging.Pdf.Tree;

/// <summary>
/// Adds invisible digital signature to a PDF page.
/// </summary>
public class PdfPage_AddInvisibleDigitalSignature
{
    public static void Run()
    {
        // get the X509 certificate from .pfx-file
        using (X509Certificate2 certificate = new X509Certificate2("TestCertificate.pfx", "test"))
        {
            // open PDF document
            using (PdfDocument pdfDocument = new PdfDocument("TestDocumentToSign.pdf"))
            {
                // get the first PDF page
                PdfPage pdfPage = pdfDocument.Pages[0];

                // add an invisible digital signature to the PDF page
                pdfPage.AddInvisibleDigitalSignature(
                    certificate, "Signature", "Approve document", false);

                // sign PDF document and save PDF document to the output file
                pdfDocument.SaveChanges("TestDocumentToSign-signed.pdf");
            }
        }
    }
}

VB.NET

Imports System.Security.Cryptography.X509Certificates
Imports Vintasoft.Imaging.Pdf
Imports Vintasoft.Imaging.Pdf.Tree

''' <summary>
''' Adds invisible digital signature to a PDF page.
''' </summary>
Public Class PdfPage_AddInvisibleDigitalSignature
    Public Shared Sub Run()
        ' get the X509 certificate from .pfx-file
        Using certificate As New X509Certificate2("TestCertificate.pfx", "test")
            ' open PDF document
            Using pdfDocument As New PdfDocument("TestDocumentToSign.pdf")
                ' get the first PDF page
                Dim pdfPage As PdfPage = pdfDocument.Pages(0)

                ' add an invisible digital signature to the PDF page
                pdfPage.AddInvisibleDigitalSignature(certificate, "Signature", "Approve document", False)

                ' sign PDF document and save PDF document to the output file
                pdfDocument.SaveChanges("TestDocumentToSign-signed.pdf")
            End Using
        End Using
    End Sub
End Class

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