Hello,

If you go to Tools / Options and select the applications tab. Scroll down to Portable Document Format ( pdf ) click on the Action value and it will open a pull down menu, select what you want to open the pdf files

Yes, I've done that. But it still doesn't change it to the "default". When I'm in Rackspace and trying to open a PDF file, it still tries to open it with Notepad or I have to browse thru to find Adobe Reader. I have a lot of attachments and I have to browse every time I want to look at a PDF file. I know I'm adding Rackspace email into the mix - but it says in Rackspace to change the default in the Firefox browser.

https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

Deleting the mimeTypes.rdf will reset all download actions to the default settings.

Type about:support in the address bar and press enter.

Under the page logo on the left side you will see Application Basics. Under this find Profile Folder. To it’s right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Locate the mimeTypes.rdffile. Then rename or delete it. Restart Firefox.

I followed these instructions as directed. Firefox created a new mimeTypes.rdf file - but it still has Notepad as the "default". Do you think Rackspace has anything to do with it?

Please refer to this : https://support.mozilla.org/en-US/kb/disable-built-pdf-viewer-and-use-another-viewer