I bet you have been wondering why the interface to PDF files in Firefox suddenly went to pot.
CNet has the article Mozilla puts native PDF viewer in Firefox 19.
I finally found the solution to bring the real Adobe Reader back to Firefox.
In Firefox go to “Tools->options->Applications”, and change the setting for “Portable Document Format (PDF)” to “Use Adobe Acrobat (in Firefox)”
If you haven’t found the trick to linking to pdf files on your local computer and have them come up in an imbedded Adobe Reader in Firefox, you just need to add the type parameter to your HTML anchor
<a type="application/pdf" href="localFile.pdf">