'PDFsharp cannot handle this PDF feature introduced with Acrobat 6' error while opening PDF file

Question

I use PDFsharp (v1.32) for merging several PDF files. I open documents using this code:

PdfDocument inputDocument = PdfReader.Open(pdfFilePath, PdfDocumentOpenMode.Import);

And while opening one document (with PDF version 1.5 (Acrobat 6.x)) I receive an exception:

An unhandled exception of type 'PdfSharp.Pdf.IO.PdfReaderException' occurred in PdfSharp.dll Additional information: Cannot handle iref streams. The current implementation of PDFsharp cannot handle this PDF feature introduced with Acrobat 6.

What can I do with it? I need to merge all files, I cannot just skip it. I tried to find solution, but found not answered or just very old feedback from PDFsharp Team that they are going to "fix it".

Answer 1

Use PDFsharp 1.50 beta 3 from December 2015 or a newer version.

https://www.nuget.org/packages/PdfSharp/1.50.4820-RC1
https://www.nuget.org/packages/PDFsharp-gdi/1.50.4820-RC1
https://www.nuget.org/packages/PDFsharp-wpf/1.50.4820-RC1

https://github.com/empira/PDFsharp

Answer 2

You can use iText5 or iText7 to remove the iref streams.

iText5 block below is pulled from http://forum.pdfsharp.net/viewtopic.php?f=2&t=693

static public PdfDocument Open(MemoryStream sourceStream)
  {
     PdfDocument outDoc = null;
     sourceStream.Position = 0;

     try
     {
        outDoc = PdfReader.Open(sourceStream, PdfDocumentOpenMode.Import);
     }
     catch (PdfSharp.Pdf.IO.PdfReaderException)
     {
        //workaround if pdfsharp doesn't support this pdf
        sourceStream.Position = 0;
        MemoryStream outputStream = new MemoryStream();
        iTextSharp.text.pdf.PdfReader reader = new iTextSharp.text.pdf.PdfReader(sourceStream);
        iTextSharp.text.pdf.PdfStamper pdfStamper = new iTextSharp.text.pdf.PdfStamper(reader, outputStream);
        pdfStamper.FormFlattening = true;
        pdfStamper.Writer.SetPdfVersion(iTextSharp.text.pdf.PdfWriter.PDF_VERSION_1_4);
        pdfStamper.Writer.CloseStream = false;
        pdfStamper.Close();

        outDoc = PdfReader.Open(outputStream, PdfDocumentOpenMode.Import);
     }

     return outDoc;
  }

I had to re-write it for iText7 (still using the old PDFSharp):

static PdfDocument CompatibleOpen(MemoryStream inputStream, PdfDocumentOpenMode openMode)
{
 PdfDocument pdfDocument = null;
 inputStream.Position = 0;

 try
 {
    pdfDocument = PdfReader.Open(inputStream, openMode);
 }
 catch (PdfSharp.Pdf.IO.PdfReaderException)
 {
    inputStream.Position = 0;
    MemoryStream outputStream = new MemoryStream();

    iText.Kernel.Pdf.WriterProperties writerProperties = new iText.Kernel.Pdf.WriterProperties();
    writerProperties.SetPdfVersion(iText.Kernel.Pdf.PdfVersion.PDF_1_4);

    iText.Kernel.Pdf.PdfReader pdfReader = new iText.Kernel.Pdf.PdfReader(inputStream);

    iText.Kernel.Pdf.PdfDocument pdfStamper = new iText.Kernel.Pdf.PdfDocument(pdfReader, new iText.Kernel.Pdf.PdfWriter(outputStream, writerProperties)); 

    iText.Forms.PdfAcroForm pdfForm = iText.Forms.PdfAcroForm.GetAcroForm(pdfStamper, true);
    if (!pdfForm.IsNull())
    {
       pdfForm.FlattenFields();
    }
    writerProperties.SetFullCompressionMode(false);

    pdfStamper.GetWriter().SetCloseStream(false);           
    pdfStamper.Close();

    pdfDocument = PdfReader.Open(outputStream, openMode);
 }
 return pdfDocument;
}

I hope this helps someone out there going through the same pain I was, and saves them a few days!!!