The pdf in this thread, for example, will not open. <BR><BR>But this one will. <BR><BR>Can someone with more skill than I examine these links to determine whether there is something about the file ...

Fix Adobe Acrobat Reader could not open PDF because it is either not a supported file type or because the file has been damaged error on PC.

Google Chrome for Android can finally open PDF files on its own without needing a third-party app, and you can try this feature now.