I've researched, cleared caches, and downloaded other PDF readers from the store to no luck ...
Since fixing a MAPS error with a Hard Reset, I've found that I can't open PDFs on my phone anymore. With Windows 10 on my Lumia 650 phone, the default/only way to see PDFs were (add still are) through EDGE.
When I click the file, whether it's on- or off-line, it would appear to proceed and open how it use to but end up saying:
Here is the converted link from an offline PDF file that accompanies the Message above (..the same prefix appears with online PDF files):
When I email this and other PDFs to myself or click on PDFs online and open them on my PC, I'm able to see the file through EDGE without problems/error/issue.
Moved from: Microsoft Edge/ PDF, EPUB, and reading/ Windows 10