/// <summary>
/// Removes all digital signatures from PDF document.
/// </summary>
/// <param name="pdfFilename">The filename of PDF document.</param>
public static void RemoveDigitalSignaturesFromPdfDocument(string pdfFilename)
{
    // open PDF document
    using (Vintasoft.Imaging.Pdf.PdfDocument document =
        new Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename))
    {
        // if PDF document has PDF interactive form
        if (document.InteractiveForm != null)
        {
            // get reference to the interactive form of PDF document
            Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentInteractiveForm form =
                document.InteractiveForm;

            // get all signature fields of PDF document
            Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormSignatureField[] signatureFields =
                form.GetSignatureFields();

            // for each signature fields
            foreach (Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormField field in signatureFields)
            {
                // remove signature field
                field.Remove();
            }

            // pack PDF document
            document.Pack();
        }
    }
}

''' <summary>
''' Removes all digital signatures from PDF document.
''' </summary>
''' <param name="pdfFilename">The filename of PDF document.</param>
Public Shared Sub RemoveDigitalSignaturesFromPdfDocument(pdfFilename As String)
    ' open PDF document
    Using document As New Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename)
        ' if PDF document has PDF interactive form
        If document.InteractiveForm IsNot Nothing Then
            ' get reference to the interactive form of PDF document
            Dim form As Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentInteractiveForm = document.InteractiveForm

            ' get all signature fields of PDF document
            Dim signatureFields As Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormSignatureField() = _
                form.GetSignatureFields()

            ' for each signature fields
            For Each field As Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormField In signatureFields
                ' remove signature field
                field.Remove()
            Next

            ' pack PDF document
            document.Pack()
        End If
    End Using
End Sub