Firefox is only supposed to make itself the viewer for PDFs if you haven't already selected another one. Sounds like the installer goofed.

Could you try the steps in this (randomly Googled) article to make Adobe Reader or Adobe Acrobat your default once again: http://www.csu.edu.au/division/dit/services/faqs/PDF_Files/make-adobe-reader-default-viewer.pdf

All the steps in the article have already been performed. Unfortunately, all the icons for PDF files remain Firfox HTML icons and the "File Type" remains "Firefox HTML document". The files open in Adobe Acrobat, as they should. The icon and file type that are the issue. They became magically transformed when Firefox 31.0 was identified as the default browser. Thanks for trying.

Hi det104, please ignore that irrelevant reply, I meant to paste into a different tab.

Could you try the "Open With" solution in this thread: https://support.mozilla.org/questions/1012877

(If Open With doesn't appear on the right-click context menu, try holding down the Shift menu when right-clicking.)

I tried this and it worked: select a .pdf, right-click, select 'open with', in new small window select 'select standard program' then 'adobe reader' and select in the lower left corner 'open this file type always with this program'. Reseult: all .pdf files on your pc are automatically opened with Adobe reader.

It is not a file opening issue. They all open in Adobe, as they should. It is the thumbnail Firefox Icon and the Firefox HTML "File type" for all Adobe files on the hard drive that is the issue. Solved by using "System Restore" at a time point before I designated Firefox as the default browser.

Hi LCKip and det104:

I'm not 100% sure from reading your two posts: Does using "Open With" fix half the problem (opener changes to Adobe but description remains inaccurate) or the whole problem (file description changes to Adobe as well)?

Hello Det104 & jscher. Due to holidays and time constraints I stop taking part in this discussion definately.