How Virtual data room works?

I was unable to configure VDR in NC22. I watched the video about configuring collabora online to show watermarks over the content and works great. But you still can download the documents without watermarks so i dont understand how it works.

The only way i found maybe has sense is sharing the content with public link, then, you can hide download buttons. But using it this way collabora online does not work (not loading, grey screen)

Also i have to edit a file to enable the watermarking functionality for PDF files, otherwise the PDF will open on PDF viewer or promp to download. I dont understand a VDR not supporting PDFs.

What is the trick to get it working?