Problems opening pdf files after uploading them as invoice files or license files.

When I use software licenses and upload pdf file, when I try to open it, it opens not the original file, but file with the name report.pdf and I get an error - something about the file being corrupt or invalid format.
I tested it in 2 different installation of latest Desktop Central, using different pdf readers (adobe, PDFXechange, Sumatra), different browsers (Firefox, IE). I also tried to download file first, but it downloads as Report.pdf (not the name I gave it originally) and it fails to open afterwards.
I do not have this problem with other, not pdf files (txt, jpg...).
I also tried to change the file name to shorter, using only English characters, uploading it from different paths and computers - to no avail.

As the feature to upload invoice and license file is very usuful to me, please try to solve it.

P.D.