Great work-around! Thanks so much for posting this. I had been really annoyed with this problem since upgrading to FF4 a while back, and then was pretty annoyed to see FF5 didn't offer native PDF support either. Followed your steps and it worked like a charm -- PDFs are now opening just fine!

Couple of quick notes:
* I had to go through your full process, as well, with that second set of steps in the Extensions folder.

* A couple of times, I had issues with OSX not reading the .xpi file as a compressed file, so I had to right-click and compress the file first, then when I un/de-compressed it, it opened the archive and made the subfolders like it was supposed to. This happened in the sixth step of the first section ('You should get a file called fx-quartz-pdf-1.2.0.xpi in your Downloads folder. Double-click it to decompress it.') and then again in the eighth step in the second section ('Back in the extensions folder, double-click on colesbury@gmail.com.xpi. This should expand it into a folder...') -- but again, just manually compressing the file so OS X saw it as an archive file did the trick.

* In addition, I also ran into a minor snag when I tried to add the extension in Firefox -- when trying to select the file in the 'Browse to and select the blahblah.xpi file you created' step, that file was grayed out. It turned out that by compressing the 6 files in the previous step, it had created the file fx-quartz-pdf-1.2.0.xpi but had renamed it with a .zip on the end and then hidden the extension. I did a 'Get Info' on the file in the Finder window and just deleted the .zip from the filename. (Note that OS X will prompt you to either use .zip or .xpi as the extension at this point, and you want to select .xpi)

Just thought I'd post these minor snags in case anyone else runs into them as well. Thanks again for posting these steps!

Hi jsr1138,

The snags you're reporting are likely the result of running the procedure under OS 10.5. This version of the OS does not recognize .xpi files as compressed files. You can get around it by renaming it with the .zip extension as you discovered and then changing back to .xpi (but do it in the Get Info dialog box or you'll run into the hidden extension problem you had).

Thanks