Hi leonmuzire96,
If I am understanding correctly, you are trying to convert a binary document to an office document on WebViewer? Which demo are you following for the conversion?
Here are the currently supported file formats for WebViewer:
The exception you see is because the file you are trying to open is not a PDF, you can see a related forum post here:
Best Regards,
Kevin Kim
Web Development Support Engineer
PDFTron Systems, Inc.
www.pdftron.com