Works for me, testing with https://www.carrferrell.com/uploads/files/deceptive-domain-solicitations.pdf Oddly, your "More System Details" shows one plugin from Acrobat/Reader 10 and another from Acrobat/Reader DC, but none for 11. You might want to remove the older one. To locate it on disk, you can type or paste '''about:plugins''' in the address bar and press Enter. This should display a long page with details about all your plugins, including the physical location of each one. You can use Find (Ctrl+f) to look for ''nppdf'' to track them down. Assuming no other application needs the plugin, you could rename the older one to have a .OLD extension instead of .DLL so Firefox doesn't run it. At least we can be sure what version you are testing.