Click 'Add-ons.' You can also hold 'SHIFT' + 'COMMAND' + 'A. Click on the three lines in the upper-right corner to open a menu. It will open your specified folder in the Finder window.
Browser plug-ins typically do not support all PDF. Installing Firefox 19 or later, for instance, can result in your Adobe plug-in being disabled and replaced.
The Internet browser at the core of the SeaMonkey Internet Application Suite uses the same rendering engine and application platform as Mozilla Firefox, with popular features like tabbed browsing, feed detection, popup blocking, smart location bar, find as you type and a lot of other functionality for a smooth web experience.
