''' <summary>
''' Signs a PDF or PDF/A document using specified certificate.
''' </summary>
''' <param name="inputFilename">The filename of input PDF document.</param>
''' <param name="outputFilename">The filename of output PDF document.</param>
''' <param name="certificate">The certificate that should be used
''' for signing the input PDF document.</param>
''' <param name="conformance">The conformance of PDF document.</param>
Public Shared Sub SignDocument(inputFilename As String, outputFilename As String, conformance As Vintasoft.Imaging.Pdf.PdfDocumentConformance, certificate As System.Security.Cryptography.X509Certificates.X509Certificate2)
    SignDocument(inputFilename, outputFilename, conformance, certificate, False, Nothing)
End Sub

''' <summary>
''' Signs with timestamp a PDF or PDF/A document using specified certificate.
''' </summary>
''' <param name="inputFilename">The filename of input PDF document.</param>
''' <param name="outputFilename">The filename of output PDF document.</param>
''' <param name="certificate">The certificate that should be used
''' for signing the input PDF document.</param>
''' <param name="addCertificateChain">A value indicating whether signing certificate chain must be added to signature.</param>
''' <param name="conformance">The conformance of PDF document.</param>
''' <param name="timestampServerUrl">Timestamp server URL.</param>
Public Shared Sub SignDocument(inputFilename As String, outputFilename As String, conformance As Vintasoft.Imaging.Pdf.PdfDocumentConformance, certificate As System.Security.Cryptography.X509Certificates.X509Certificate2, addCertificateChain As Boolean, timestampServerUrl As String)
    Dim converter As Vintasoft.Imaging.Pdf.Processing.PdfDocumentConverter = Nothing

    ' if PDF document conformance is specified
    If conformance <> Vintasoft.Imaging.Pdf.PdfDocumentConformance.Undefined Then
        ' create PDF document converter
        converter = Vintasoft.Imaging.Pdf.Processing.PdfDocumentConverter.Create(conformance)

        ' if is PDF/A converter
        Dim pdfAConverter As Vintasoft.Imaging.Pdf.Processing.PdfA.PdfAConverter = TryCast(converter, Vintasoft.Imaging.Pdf.Processing.PdfA.PdfAConverter)
                ' set ICC profiles
                'pdfAConverter.DefaultCmykIccProfileFilename = "DefaultCMYK.icc";
                'pdfAConverter.DefaultRgbIccProfileFilename = "DefaultRGB.icc";
        If pdfAConverter IsNot Nothing Then
        End If

        ' if PDF document converter is not found
        If converter Is Nothing Then
            Dim message As String = String.Format("Unsupported {0} conformance.", conformance)
            Throw New System.ArgumentOutOfRangeException(message)
        End If
    End If

    ' open PDF document
    Using document As New Vintasoft.Imaging.Pdf.PdfDocument(inputFilename)
        ' add signature
        AddSignature(document, certificate, addCertificateChain, timestampServerUrl, 1)

        ' if PDF document cannot be converted
        If converter Is Nothing Then
            If inputFilename = outputFilename Then
                ' sign PDF document and save changes in PDF document
                document.SaveChanges()
            Else
                ' sign PDF document and save PDF document to the output file
                document.SaveChanges(outputFilename)
            End If
        Else
            If inputFilename <> outputFilename Then
                Dim pdfAConverter As Vintasoft.Imaging.Pdf.Processing.PdfA.PdfAConverter = DirectCast(converter, Vintasoft.Imaging.Pdf.Processing.PdfA.PdfAConverter)
                pdfAConverter.OutputFilename = outputFilename
            End If

            ' sign and convert PDF document
            Dim conversionResult As Vintasoft.Imaging.Processing.ConversionProfileResult = converter.Convert(document, New Vintasoft.Imaging.Processing.ProcessingState())

            ' if conversion falied
            If Not conversionResult.IsSuccessful Then
                ' throw conversion exception
                Throw conversionResult.CreateConversionException()
            End If
        End If
    End Using
End Sub

''' <summary>
''' Adds a digital signature to specified PDF document.
''' </summary>
''' <param name="document">The PDF document.</param>
''' <param name="certificate">The certificate that should be added.</param>
''' <param name="timestampServerUrl">Timestamp server URL.</param>
''' <param name="addCertificateChain">A value indicating whether signing certificate chain must be added to signature.</param>
''' <param name="sigNumber">The number of signature field.</param>
Private Shared Sub AddSignature(document As Vintasoft.Imaging.Pdf.PdfDocument, certificate As System.Security.Cryptography.X509Certificates.X509Certificate2, addCertificateChain As Boolean, timestampServerUrl As String, sigNumber As Integer)
    ' if PDF document does not have interactive form
    If document.InteractiveForm Is Nothing Then
        ' create the interactive form in document
        document.InteractiveForm = New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentInteractiveForm(document)
    End If

    ' specify that document contains signatures
    document.InteractiveForm.SignatureFlags = Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentSignatureFlags.SignaturesExist Or Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentSignatureFlags.AppendOnly

    ' specify that the viewer application must NOT construct appearance streams and
    ' appearance properties for widget annotations in the document
    document.InteractiveForm.NeedAppearances = False

    ' get PDF page on which signature will be placed
    Dim page As Vintasoft.Imaging.Pdf.Tree.PdfPage = document.Pages(0)

    ' calculate the signature field rectangle (field will be placed in the bottom-center of page)
    Dim signatureRect As New System.Drawing.RectangleF()
    signatureRect.Width = page.MediaBox.Width / 5
    signatureRect.Height = signatureRect.Width / 3
    signatureRect.X = page.MediaBox.X + (page.MediaBox.Width - signatureRect.Width) / 2
    signatureRect.Y = page.MediaBox.Y + signatureRect.Height * sigNumber

    ' create parameters for creation of PKCS#7 signature
    Dim creationParams As New Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfPkcsSignatureCreationParams(certificate, addCertificateChain)
    ' if timestamp server is specified
    If Not String.IsNullOrEmpty(timestampServerUrl) Then
        ' specify the timestamp authority client
        creationParams.TimestampAuthorityClient = New Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.TimestampAuthorityWebClient(timestampServerUrl)
    End If

    ' create PKCS#7 signature
    Dim signature As Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfPkcsSignature = Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfPkcsSignature.CreatePkcs7Signature(document.Format, creationParams)

    ' create signature info
    Dim signatureInfo As New Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfSignatureInformation(document, signature)
    signatureInfo.SignerName = certificate.GetNameInfo(System.Security.Cryptography.X509Certificates.X509NameType.SimpleName, False)
    signatureInfo.Reason = "Test signing"
    signatureInfo.Location = System.Globalization.CultureInfo.CurrentCulture.EnglishName
    signatureInfo.SigningTime = System.DateTime.Now

    ' create the signature field
    Dim signatureField As New Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormSignatureField(document, String.Format("MySignature{0}", sigNumber), signatureRect)

    ' set the signature information
    signatureField.SignatureInfo = signatureInfo

    ' create the signature appearance
    Using g As Vintasoft.Imaging.Pdf.Drawing.PdfGraphics = signatureField.CreateAppearanceGraphics()
        ' signature text
        Dim signatureText As String = String.Format("Digitally signed by" & vbLf & "{0}", signatureInfo.SignerName)

        ' signature appearance rect
        Dim rect As New System.Drawing.RectangleF(System.Drawing.PointF.Empty, signatureField.Annotation.Rectangle.Size)

        ' draw background
        g.FillRectangle(New Vintasoft.Imaging.Pdf.Drawing.PdfBrush(System.Drawing.Color.FromArgb(255, System.Drawing.Color.Lime)), rect)

        ' padding
        rect.Inflate(-rect.Height / 10, -rect.Height / 10)

        ' create TimesRoman font
        Dim font As Vintasoft.Imaging.Pdf.Tree.Fonts.PdfFont = document.FontManager.GetStandardFont(Vintasoft.Imaging.Pdf.Tree.Fonts.PdfStandardFontType.TimesRoman)

        ' measure font size
        Dim fontSize As Single = g.MeasureFontSize(signatureText, font, rect.Width, rect.Height)

        ' draw signture text
        g.DrawString(signatureText, font, fontSize, New Vintasoft.Imaging.Pdf.Drawing.PdfBrush(System.Drawing.Color.Black), rect, Vintasoft.Imaging.Pdf.Drawing.PdfContentAlignment.Center, _
            False)
    End Using

    ' add signature field to the interactive form of document
    document.InteractiveForm.Fields.Add(signatureField)

    ' if PDF page does not have annotations
    If page.Annotations Is Nothing Then
        ' create an empty annotation collection for page
        page.Annotations = New Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationList(document)
    End If
    ' add widget annotation of signature field to the annotation collection of page
    page.Annotations.Add(signatureField.Annotation)
End Sub

/// <summary>
/// Signs a PDF or PDF/A document using specified certificate.
/// </summary>
/// <param name="inputFilename">The filename of input PDF document.</param>
/// <param name="outputFilename">The filename of output PDF document.</param>
/// <param name="certificate">The certificate that should be used
/// for signing the input PDF document.</param>
/// <param name="conformance">The conformance of PDF document.</param>
public static void SignDocument(
    string inputFilename,
    string outputFilename,
    Vintasoft.Imaging.Pdf.PdfDocumentConformance conformance,
    System.Security.Cryptography.X509Certificates.X509Certificate2 certificate)
{
    SignDocument(inputFilename, outputFilename, conformance, certificate, false, null);
}

/// <summary>
/// Signs with timestamp a PDF or PDF/A document using specified certificate.
/// </summary>
/// <param name="inputFilename">The filename of input PDF document.</param>
/// <param name="outputFilename">The filename of output PDF document.</param>
/// <param name="certificate">The certificate that should be used
/// for signing the input PDF document.</param>
/// <param name="addCertificateChain">A value indicating whether signing certificate chain must be added to signature.</param>
/// <param name="conformance">The conformance of PDF document.</param>
/// <param name="timestampServerUrl">Timestamp server URL.</param>
public static void SignDocument(
    string inputFilename,
    string outputFilename,
    Vintasoft.Imaging.Pdf.PdfDocumentConformance conformance,
    System.Security.Cryptography.X509Certificates.X509Certificate2 certificate,
    bool addCertificateChain,
    string timestampServerUrl)
{
    Vintasoft.Imaging.Pdf.Processing.PdfDocumentConverter converter = null;

    // if PDF document conformance is specified
    if (conformance != Vintasoft.Imaging.Pdf.PdfDocumentConformance.Undefined)
    {
        // create PDF document converter
        converter = Vintasoft.Imaging.Pdf.Processing.PdfDocumentConverter.Create(conformance);

        // if is PDF/A converter
        Vintasoft.Imaging.Pdf.Processing.PdfA.PdfAConverter pdfAConverter = converter as Vintasoft.Imaging.Pdf.Processing.PdfA.PdfAConverter;
        if (pdfAConverter != null)
        {
            // set ICC profiles
            //pdfAConverter.DefaultCmykIccProfileFilename = "DefaultCMYK.icc";
            //pdfAConverter.DefaultRgbIccProfileFilename = "DefaultRGB.icc";
        }

        // if PDF document converter is not found
        if (converter == null)
        {
            string message = string.Format("Unsupported {0} conformance.", conformance);
            throw new System.ArgumentOutOfRangeException(message);
        }
    }

    // open PDF document
    using (Vintasoft.Imaging.Pdf.PdfDocument document = new Vintasoft.Imaging.Pdf.PdfDocument(inputFilename))
    {
        // add signature
        AddSignature(document, certificate, addCertificateChain, timestampServerUrl, 1);

        // if PDF document cannot be converted
        if (converter == null)
        {
            if (inputFilename == outputFilename)
            {
                // sign PDF document and save changes in PDF document
                document.SaveChanges();
            }
            else
            {
                // sign PDF document and save PDF document to the output file
                document.SaveChanges(outputFilename);
            }
        }
        else
        {
            if (inputFilename != outputFilename)
            {
                Vintasoft.Imaging.Pdf.Processing.PdfA.PdfAConverter pdfAConverter =
                    (Vintasoft.Imaging.Pdf.Processing.PdfA.PdfAConverter)converter;
                pdfAConverter.OutputFilename = outputFilename;
            }

            // sign and convert PDF document
            Vintasoft.Imaging.Processing.ConversionProfileResult conversionResult =
                converter.Convert(document, new Vintasoft.Imaging.Processing.ProcessingState());

            // if conversion falied
            if (!conversionResult.IsSuccessful)
            {
                // throw conversion exception
                throw conversionResult.CreateConversionException();
            }
        }
    }
}

/// <summary>
/// Adds a digital signature to specified PDF document.
/// </summary>
/// <param name="document">The PDF document.</param>
/// <param name="certificate">The certificate that should be added.</param>
/// <param name="timestampServerUrl">Timestamp server URL.</param>
/// <param name="addCertificateChain">A value indicating whether signing certificate chain must be added to signature.</param>
/// <param name="sigNumber">The number of signature field.</param>
private static void AddSignature(
    Vintasoft.Imaging.Pdf.PdfDocument document,
    System.Security.Cryptography.X509Certificates.X509Certificate2 certificate,
    bool addCertificateChain,
    string timestampServerUrl,
    int sigNumber)
{
    // if PDF document does not have interactive form
    if (document.InteractiveForm == null)
    {
        // create the interactive form in document
        document.InteractiveForm = new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentInteractiveForm(document);
    }

    // specify that document contains signatures
    document.InteractiveForm.SignatureFlags =
        Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentSignatureFlags.SignaturesExist |
        Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfDocumentSignatureFlags.AppendOnly;

    // specify that the viewer application must NOT construct appearance streams and
    // appearance properties for widget annotations in the document
    document.InteractiveForm.NeedAppearances = false;

    // get PDF page on which signature will be placed
    Vintasoft.Imaging.Pdf.Tree.PdfPage page = document.Pages[0];

    // calculate the signature field rectangle (field will be placed in the bottom-center of page)
    System.Drawing.RectangleF signatureRect = new System.Drawing.RectangleF();
    signatureRect.Width = page.MediaBox.Width / 5;
    signatureRect.Height = signatureRect.Width / 3;
    signatureRect.X = page.MediaBox.X + (page.MediaBox.Width - signatureRect.Width) / 2;
    signatureRect.Y = page.MediaBox.Y + signatureRect.Height * sigNumber;

    // create parameters for creation of PKCS#7 signature
    Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfPkcsSignatureCreationParams creationParams =
        new Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfPkcsSignatureCreationParams(certificate, addCertificateChain);
    // if timestamp server is specified
    if (!string.IsNullOrEmpty(timestampServerUrl))
    {
        // specify the timestamp authority client
        creationParams.TimestampAuthorityClient = new Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.TimestampAuthorityWebClient(timestampServerUrl);
    }

    // create PKCS#7 signature
    Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfPkcsSignature signature = Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfPkcsSignature.CreatePkcs7Signature(
         document.Format, creationParams);

    // create signature info
    Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfSignatureInformation signatureInfo =
        new Vintasoft.Imaging.Pdf.Tree.DigitalSignatures.PdfSignatureInformation(document, signature);
    signatureInfo.SignerName = certificate.GetNameInfo(
        System.Security.Cryptography.X509Certificates.X509NameType.SimpleName, false);
    signatureInfo.Reason = "Test signing";
    signatureInfo.Location = System.Globalization.CultureInfo.CurrentCulture.EnglishName;
    signatureInfo.SigningTime = System.DateTime.Now;

    // create the signature field
    Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormSignatureField signatureField =
        new Vintasoft.Imaging.Pdf.Tree.InteractiveForms.PdfInteractiveFormSignatureField(document, string.Format("MySignature{0}", sigNumber), signatureRect);

    // set the signature information
    signatureField.SignatureInfo = signatureInfo;

    // create the signature appearance
    using (Vintasoft.Imaging.Pdf.Drawing.PdfGraphics g = signatureField.CreateAppearanceGraphics())
    {
        // signature text
        string signatureText = string.Format("Digitally signed by\n{0}",
            signatureInfo.SignerName);

        // signature appearance rect
        System.Drawing.RectangleF rect = new System.Drawing.RectangleF(
            System.Drawing.PointF.Empty,
            signatureField.Annotation.Rectangle.Size);

        // draw background
        g.FillRectangle(new Vintasoft.Imaging.Pdf.Drawing.PdfBrush(
            System.Drawing.Color.FromArgb(255, System.Drawing.Color.Lime)), rect);

        // padding
        rect.Inflate(-rect.Height / 10, -rect.Height / 10);

        // create TimesRoman font
        Vintasoft.Imaging.Pdf.Tree.Fonts.PdfFont font = document.FontManager.GetStandardFont(
            Vintasoft.Imaging.Pdf.Tree.Fonts.PdfStandardFontType.TimesRoman);

        // measure font size
        float fontSize = g.MeasureFontSize(signatureText, font, rect.Width, rect.Height);

        // draw signture text
        g.DrawString(
            signatureText,
            font, fontSize, new Vintasoft.Imaging.Pdf.Drawing.PdfBrush(System.Drawing.Color.Black),
            rect, Vintasoft.Imaging.Pdf.Drawing.PdfContentAlignment.Center, false);
    }

    // add signature field to the interactive form of document
    document.InteractiveForm.Fields.Add(signatureField);

    // if PDF page does not have annotations
    if (page.Annotations == null)
        // create an empty annotation collection for page
        page.Annotations = new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationList(document);
    // add widget annotation of signature field to the annotation collection of page
    page.Annotations.Add(signatureField.Annotation);
}