''' <summary>
''' Exports all PDF annotations of PDF document to the file in XFDF format.
''' </summary>
''' <param name="pdfFilename">The name of PDF file.</param>
''' <param name="xfdfFilename">The name of XFDF filen.</param>
Public Shared Sub ExportPdfAnnotationsToXfdf(pdfFilename As String, xfdfFilename As String)
    ' open PDF document
    Using document As New Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename)
        ' create XFDF codec
        Dim xfdfCodec As New Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationXfdfCodec()

        ' create file
        Using stream As System.IO.Stream = System.IO.File.Create(xfdfFilename)
            ' export all PDF annotations of PDF document to the file in XFDF format
            xfdfCodec.Export(document, stream)
        End Using
    End Using
End Sub

''' <summary>
''' Imports the PDF annotations from XFDF format.
''' </summary>
''' <param name="pdfFilename">The name of PDF file.</param>
''' <param name="xfdfFilename">The name of XFDF file.</param>
Public Shared Sub ImportPdfAnnotationsFromXfdf(pdfFilename As String, xfdfFilename As String)
    ' open PDF document
    Using document As New Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename)
        ' create XFDF codec
        Dim xfdfCodec As New Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationXfdfCodec()

        ' open XFDF file
        Using stream As System.IO.Stream = System.IO.File.OpenRead(xfdfFilename)
            ' import the PDF annotations from XFDF file
            xfdfCodec.Import(document, stream)
        End Using

        ' save changes in PDF document
        document.SaveChanges()
    End Using
End Sub

/// <summary>
/// Exports all PDF annotations of PDF document to the file in XFDF format.
/// </summary>
/// <param name="pdfFilename">The name of PDF file.</param>
/// <param name="xfdfFilename">The name of XFDF filen.</param>
public static void ExportPdfAnnotationsToXfdf(string pdfFilename, string xfdfFilename)
{
    // open PDF document
    using (Vintasoft.Imaging.Pdf.PdfDocument document = new Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename))
    {
        // create XFDF codec
        Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationXfdfCodec xfdfCodec =
            new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationXfdfCodec();

        // create file
        using (System.IO.Stream stream = System.IO.File.Create(xfdfFilename))
        {
            // export all PDF annotations of PDF document to the file in XFDF format
            xfdfCodec.Export(document, stream);
        }
    }
}

/// <summary>
/// Imports the PDF annotations from XFDF format.
/// </summary>
/// <param name="pdfFilename">The name of PDF file.</param>
/// <param name="xfdfFilename">The name of XFDF file.</param>
public static void ImportPdfAnnotationsFromXfdf(string pdfFilename, string xfdfFilename)
{
    // open PDF document
    using (Vintasoft.Imaging.Pdf.PdfDocument document = new Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename))
    {
        // create XFDF codec
        Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationXfdfCodec xfdfCodec =
            new Vintasoft.Imaging.Pdf.Tree.Annotations.PdfAnnotationXfdfCodec();

        // open XFDF file
        using (System.IO.Stream stream = System.IO.File.OpenRead(xfdfFilename))
        {
            // import the PDF annotations from XFDF file
            xfdfCodec.Import(document, stream);
        }

        // save changes in PDF document
        document.SaveChanges();
    }
}