Setting Firefox To Use the Full PDF Program to view PDFs
Firefox often wants to open PDFs in the browser. This is generally an issue as the plugin is not always installed for Firefox, or causes crashes in Firefox. We recommend setting Firefox to open PDFs in the PDF viewing program.
Click on the Firefox Menu, select Options, Options.
Click on the Applications Tab. Look or search for "Adobe Acrobat Document" OR "PDF-X-Change Viewer Document".
Change the dropdown from "Use Adobe Acrobat (in Firefox)" to "Use Other". A dialog box will appear.