Hello Vladimir,
sorry for the late answer...
Once again huge thanks for attending to this problem.
I have now verified that the problem is indeed with that very test document (or with the way how it was created). I used different PDF printers to check the situation: if created with one PDF printer the stripped text from the PDF doc would contain that odd chars whereas if PDF document was created with another PDF printer stripped text would contain regular characters.
I also noticed that PDF stripper seems to be quite unreliable when there are various contents in the PDF document. If document contains e.g. a table with text in it, the stripped text would always contain only odd chars.
Therefore I might need to be looking for a more reliable way to strip text from PDF documents.
Thanks again for all your help,
Marin