Issues with PDFs and browsers

It seems that I have issues with viewing PDF-files on my web browser when I try to access them from my home. The problem exists regardless of the browser, be it Opera or Chrome. I use laptop HP with Windows 10. The PDFs are downloaded successfully, but then they can’t be opened and viewed in the browser. I tried different proxies and two VPNs (Hola VPN and Betternet). Maybe, this problem caused by VPNs? Whether solutions reviewed here can help me with the issue?

Thanks in advance!