Hmm, perhaps it's a setting or add-on issue. To rule that out, could you try this: '''New Profile Test''' This takes about 3 minutes, plus the time to test some problem links. Inside Firefox, type or paste '''about:profiles''' in the address bar and press Enter/Return to load it. Click the Create a New Profile button, then click Next. Assign a name like Oct2018, ignore the option to relocate the profile folder, and click the Finish button. After creating the profile, scroll down to it and click the '''Set as default profile''' button below that profile, then scroll back up and click the '''Restart normally''' button. (There are some other buttons, but please ignore them.) Firefox should exit and then start up using the new profile, which will just look brand new. Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system so we can get a clean test. You will need to go to the Options page, Applications list and update your PDF preference to opening in Nitro PDF before testing. ''Do the links work any better in the new profile?'' When you are done with the experiment, open the about:profiles page again, click the '''Set as default profile''' button for your normal profile, then click the '''Restart normally''' button to get back to it.