It seems to be an issue with the NPAPI plugin Adobe released, it just isn't working. 

We were able to get it working with 'PDF Plugin for Firefox on Mac OS X'.  Based on posts on the Mozilla forums there are other plugins that work.  Some posts indicate it is a compatiblity issue with Firefox 3 but we tested with Firefox 5 and Firefox 10 and it didn't work there either.

AntD00d wrote:

 

http://helpx.adobe.com/content/dam/help/attachments/Acrobat_Reader_Rel easeNote_10.1.3.pdf says it dropped old Firefox versions.

It's not about that, I think, as I got the exactly same bug with Firefox 12.0 / OS X 10.7.3 after the last Adobe Reader update.

However, the release notes are interesting, see p. 6: "If you still require a 32-bit solution, this update also supports Mozilla Firefox for Macintosh when it is opened in 32-bit mode." 

So, it seems that the last update is pushing the inline viewer (NPAPI?) plugin to 64-bit Firefox, even that it's known that it wouldn't work. In Mozilla forums some had tried to fix this by forcing Firefox to open in 32-bit mode (via Finder -> Applications -> right-click Firefox -> Get Info -> check Open in 32-bit mode), but I'd rather see the bug itself fixed.

AntD00d wrote:

 

juhanaven wrote:

 

AntD00d wrote:

 

http://helpx.adobe.com/content/dam/help/attachments/Acrobat_Reader_Rel easeNote_10.1.3.pdf says it dropped old Firefox versions.

 

It's not about that, I think, as I got the exactly same bug with Firefox 12.0 / OS X 10.7.3 after the last Adobe Reader update.

 

However, the release notes are interesting, see p. 6: "If you still require a 32-bit solution, this update also supports Mozilla Firefox for Macintosh when it is opened in 32-bit mode." 

 

So, it seems that the last update is pushing the inline viewer (NPAPI?) plugin to 64-bit Firefox, even that it's known that it wouldn't work. In Mozilla forums some had tried to fix this by forcing Firefox to open in 32-bit mode (via Finder -> Applications -> right-click Firefox -> Get Info -> check Open in 32-bit mode), but I'd rather see the bug itself fixed.

Interesting. Where are you seeing this in Mozilla forums? I didn't see anyone talk about this Adobe Reader problem in Firefox newsgroups on news.mozilla.org news server even after I posted my issue.

It's in this bug report: http://support.mozilla.org/fi/questions/925055 - confirmed already by 230 people, by the way...

Sorry to hear that the 32-bit workaround didn't work for you. (I haven't even tested it yet myself, just disabled the plug-in altogether to get the pdf files even loaded to Preview...)

I have the updated Firefox (10.0.3) and just updated Adobe reader to 10.1.3 - after the update, I can't open Adobe files in Firefox. I can open previously downloaded files fine, and can open new ones in Safari. I looked up the PDF plug-in for Firefox mentioned above, but that's for earlier versions of Firefox. So - should I just use Safari when there's a .pdf file until Adobe gets rid of the bug, or is there anything I can do?

Thanks! Opening it in 32-bit mode worked! I appreciate the detailed instructions.   Oh, and it's Mac 10.7.3.

Nice that Mozilla actually has a way to report these issues to people who might notice. Is there any way to submit a bug to Adobe to the tune of "Reader doesn't work in 64-bit Firefox 12 on OS X" and actually have them listen? These forums sometimes feel like the elevators that have installed a non-working "Close Door" button just to placate you.