''' <summary>
''' Converts a PDF document to conformance with PDF/A-1b specification.
''' </summary>
''' <param name="pdfFilename">The filename of source PDF document.</param>
''' <param name="outputPdfFilename">The filename of output PDF document.</param>
Public Shared Sub ConvertDocumentToPdfA1b(pdfFilename As String, outputPdfFilename As String)
    ' determine that file must converted to the PDF/A-1b and saved back to the source file
    Dim sameFile As Boolean = pdfFilename.ToUpperInvariant() = outputPdfFilename.ToUpperInvariant()
    ' if converted PDF document must NOT be saved to the source file
    If Not sameFile Then
        ' copy the source file to the output file
        System.IO.File.Copy(pdfFilename, outputPdfFilename, True)
    End If

    System.Console.WriteLine("Conversion...")
    ' open the output PDF document
    Using document As New Vintasoft.Imaging.Pdf.PdfDocument(outputPdfFilename)
        ' convert the PDF document to conformance with the PDF/A-1b format
        Try
            document.ConvertDocument(Vintasoft.Imaging.Pdf.PdfDocumentConformance.PdfA_1b)
            System.Console.WriteLine("Document converted to PDF/A-1b.")
        Catch ex As System.Exception
            If Not sameFile Then
                System.IO.File.Delete(outputPdfFilename)
            End If
            System.Console.WriteLine(String.Format("Cannot convert document to PDF/A-1b: {0}", ex.Message))
        End Try
    End Using
End Sub

/// <summary>
/// Converts a PDF document to conformance with PDF/A-1b specification.
/// </summary>
/// <param name="pdfFilename">The filename of source PDF document.</param>
/// <param name="outputPdfFilename">The filename of output PDF document.</param>
public static void ConvertDocumentToPdfA1b(string pdfFilename, string outputPdfFilename)
{
    // determine that file must converted to the PDF/A-1b and saved back to the source file
    bool sameFile = pdfFilename.ToUpperInvariant() == outputPdfFilename.ToUpperInvariant();
    // if converted PDF document must NOT be saved to the source file
    if (!sameFile)
        // copy the source file to the output file
        System.IO.File.Copy(pdfFilename, outputPdfFilename, true);

    System.Console.WriteLine("Conversion...");
    // open the output PDF document
    using (Vintasoft.Imaging.Pdf.PdfDocument document = new Vintasoft.Imaging.Pdf.PdfDocument(outputPdfFilename))
    {
        // convert the PDF document to conformance with the PDF/A-1b format
        try
        {
            document.ConvertDocument(Vintasoft.Imaging.Pdf.PdfDocumentConformance.PdfA_1b);
            System.Console.WriteLine("Document converted to PDF/A-1b.");
        }
        catch (System.Exception ex)
        {
            if (!sameFile)
                System.IO.File.Delete(outputPdfFilename);
            System.Console.WriteLine(string.Format("Cannot convert document to PDF/A-1b: {0}", ex.Message));
        }
    }
}