I recently updated to Firefox 19.0.
In Firefox, under "options" all the Adobe types have always been marked as "SAVE FILE" as you see in the attached image.
In the FF Add-Ons manager, Adobe Acrobat is listed as currrent (version 10.1.6.1) and I've ensured that it is marked 'DISABLED".
However, now every time I click on a pdf file it opens in the browser. That NEVER happened before. What gives?