PDFsharp & MigraDoc Foundation

I am using a C# project called ConcatenateDocuments. it is using itextsharp 4.1.6 and PDFsharp-wpf.
the users are getting this error: "The current implementation of PDFsharp cannot handle this PDF feature introduced with Acrobat 6."
what should be done in order to update the itextsharp version and where do I download please?

Maybe you have to invoke iTextSharp.
See also:
viewtopic.php?p=6703#p6703

Or try PDFsharp 1.50 beta.

_________________
Regards
Thomas Hoevel
PDFsharp Team

I get an error trying to invoke ItextSharp with code in the link you provided:
Could not load file or assembly 'itextsharp, Version=5.1.1.0, Culture=neutral,
PublicKeyToken=8354ae6d2174ddca' or one of its dependencies.
The located assembly's manifest definition does not match the assembly reference.
(Exception from HRESULT: 0x80131040)

what .NET framework do I have to run ?