Why cant my phone view PDF files?

[AC Question]

Im trying to view PDFs via the links on my campus website. Used to be able to view those PDFs on my phone a couple months ago but now it always read them as "invalid format". BTW I can view these PDF files just fine on PC. Using apps like Adobe Acrobat Reader or Google PDF Reader was pointless because I cant even download and save the PDFs into my phone storage.

Id like to know what made my phone unable to view PDFs as it normally would.

 

[the tall guy]

Hi, it might be the website you're downloading them from that has changed - are you able to download the file on the PC then send it to your phone to see if that works?