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

''' <summary>
''' Adds invisible digital signature to a PDF page.
''' </summary>
Public Class PdfPageDigitalSignatureHelper_InvisibleAppearance
    ''' <summary>
    ''' Signs a PDF document using specified PFX file.
    ''' </summary>
    ''' <param name="inputFilename">The name of input PDF file.</param>
    ''' <param name="outputFilename">The name of output PDF file.</param>
    ''' <param name="pfxFileName">The name of PFX file.</param>
    ''' <param name="pfxFilePassword">The password for PDF file.</param>
    Public Shared Sub SignPdfDocument(inputFilename As String, outputFilename As String, pfxFileName As String, pfxFilePassword As String)
        ' get the X509 certificate from .pfx-file
        Using certificate As New X509Certificate2(pfxFileName, pfxFileName)
            ' create a helper that alows 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(inputFilename, outputFilename, 0)
        End Using
    End Sub
End Class

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

/// <summary>
/// Adds invisible digital signature to a PDF page.
/// </summary>
public class PdfPageDigitalSignatureHelper_InvisibleAppearance
{
    /// <summary>
    /// Signs a PDF document using specified PFX file.
    /// </summary>
    /// <param name="inputFilename">The name of input PDF file.</param>
    /// <param name="outputFilename">The name of output PDF file.</param>
    /// <param name="pfxFileName">The name of PFX file.</param>
    /// <param name="pfxFilePassword">The password for PDF file.</param>
    public static void SignPdfDocument(
        string inputFilename,
        string outputFilename,
        string pfxFileName,
        string pfxFilePassword)
    {
        // get the X509 certificate from .pfx-file
        using (X509Certificate2 certificate = new X509Certificate2(pfxFileName, pfxFileName))
        {
            // create a helper that alows 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(inputFilename, outputFilename, 0);
        }
    }
}