Dear Stefano ....
First thanks, thanks, thanks .... and again thanks for your great work (PDFClown) and professional programming
i am a C# programmer and almost know PDF format (i studied Adobe PDF Specification 3 years ago)
i am working on an application that focused on unicode feature of PDF ....
here, there are some PDF files that in arabic or some other languages that in them , the ToUnicode stream of fonts are incorrect thus, all converting applications in word will convert these files with wrong output and content of output files are not readable.
so, my application should change (edit) these pdf's ToUnicode stream. i calculated valid ToUnicode table and now, i have valid and correct ToUnicode stream.
my problem is only replacement of this stream with old one (replace my new ToUnicode stream with existing PDF's ToUnicode stream) .
I know, in PDF every modification and editing will not remove existing objects. instead of removing or replacing content of object's stream, a new object with same ID will generate in PDF and then a new XRef Table with new Trailer will append to the end of PDF file.
Now , my question :
Is there a solution in  PDFClown to do it for me ?
in  other word, can PDFClown has define new ToUnicode (or any object) stream and append it to existing PDF and then write new XRef and Trailer to the file .
Please help me ...  if there is a way , please write a small sample in C#
again, thank you for your support.