1) If Firefox is opening PDF files with the built-in viewer and you would rather use Adobe Reader, see View PDF files in Firefox or choose another viewer

2) To reset Adobe Reader as the default PDF application, even when you open a PDF file using Windows Explorer:

Open Adobe Reader, go to Edit -> Preferences -> General and use the option, "Select Default PDF Handler". Select Adobe Reader XI, as shown below, then reboot. Ref:

• /questions/1014919#answer-618531

Note that Firefox will only try to take over some file extensions if Firefox is set as the default browser, so you may want to consider to set another browser as such.

You may have to reset this pref and possibly disable the internal PDF Viewer.

• plugin.disable_full_page_plugin_for_types: application/pdf,application/vnd.adobe.xfdf,application/vnd.fdf,application/vnd.adobe.xdp+xml

You can set the pdfjs.disabled pref to true on the about:config page to disable the build-in PDF viewer altogether.

See also:

• Tools > Options > Applications
• http://kb.mozillazine.org/File_types_and_download_actions

For the record, here's the bug report on Firefox associating itself with PDF files on Windows, even though Adobe Reader is already set as the default:

• Bug 1049521 - Be less aggressive about non-primary file type associations in Firefox on Windows

(Read Bugzilla Etiquette before commenting in bugs)

kevincrath, Were you able to solve the problem using any of the suggested fixes, or do you still need more help?

Note that a fix for bug 1049521 was just uplifted to Firefox 33 so make sure you update Firefox to the latest version.

this problem still exists. I tried all fixes suggested and still will not open pdf files of any kind since update. win 7 ff update 33

When you open a PDF file that you saved to your computer, by double-clicking the file, does it open with Adobe Reader or with Firefox?

If the PDF file opens with Adobe Reader then follow the instructions in View PDF files in Firefox or choose another viewer to set Adobe Reader as the application for Portable Document Format (PDF) in your Firefox Options for Applications.

If the PDF file opens in Firefox when you open it from your hard drive, even though you have Firefox 33 installed, try uninstalling and reinstalling Firefox:

1. Download the latest Firefox version (currently 33.1.1) from mozilla.org and save the setup file to your computer.
   • Note: You can use this link for the online (stub) installer or choose the full installer for your operating system and language from this page.
2. After the download finishes, close all Firefox windows (or open the Firefox menu and click the Exit button ).
3. Uninstall Firefox from your computer.
4. Reinstall Firefox using the setup file you downloaded before.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data.

The above instructions were meant for kevincrath, the thread owner. (I mistook the post from xtroop as coming from the thread owner).

To xtroop: You have asked a question in a thread that doesn't belong to you. See Mozilla Support rules and guidelines: Do not re-use existing threads started by others, even if they are seemingly on the same subject. Ask a new question instead.

If you've already tried resetting Adobe Reader as the default PDF application (Open Adobe Reader, go to Edit -> Preferences -> General and use the option, "Select Default PDF Handler"; Select Adobe Reader XI, reboot) as well as the other suggestions in this thread then you should ask a new question.