Hi Jonathan, I'm curious where you saw those instructions? If that's on Adobe's site now, Mozilla should encourage them to update that. ''Meanwhile:'' Firefox used to automatically install any extension that the software publisher listed in the Windows Registry. It doesn't do that any more. The publisher is supposed to give users an install link instead. Until Adobe provides working instructions, we have to improvise... I have the non-subscription version, Acrobat 2017, so the extension XPI file is located here: C:\Program Files (x86)\Adobe\'''Acrobat 2017'''\Acrobat\Browser\WCFirefoxExtn\WebExtn\signed_extn With DC, the bolded part probably is different, but the other part probably is the same. If you can find that folder and the XPI file -- for reference mine is named adobe_acrobat-1.0-windows.xpi -- then you can install it this way: Open the Add-ons page using either: * Ctrl+Shift+a (Mac: Command+Shift+a) * "3-bar" menu button (or Tools menu) > Add-ons * type or paste '''about:addons''' in the address bar and press Enter/Return In the left column of the Add-ons page, click Extensions. On the right side, find the "gear" button and click that to open a menu, then click "Install Add-on From File". You'll need to point Firefox to that folder to grab the file. Alternately, it may work to drag-and-drop that file onto a tab. I didn't think it was working when I tested because there was a delay, but eventually Firefox asked if I granted permissions so it actually did work.