I am wondering how I can see PDF files or add PDF files to shared articles with me. Thank you-
At the moment only the owner of the shared item can add a PDF to it. Two conditions must be met for you to see a PDF: (1) The owner must have added a PDF to the shared item and (2) he must have synced his/her library to Google Drive.
Corruption may be one of the reason if you cannot access your PDF files. I also gone through with the same problem and one of my friend suggested me to use Sysinfo PDF recovery Software. The software is easy to use and backup all the corrupted pdf files easily.
I hope my answer will be valuable to you.