(1) I created a document in Open Office Writer.  By the way, I use Windows 7.
(2) In Open Office Writer, I converted the document to a PDF file.
(3) I double-clicked on the PDF file and automatically opened the PDF file with Abobe READER.
(4) However, when I opened a webpage in my computer -using Firefox- and I retrieved the PDF file from a link in the webpage, the PDF file was displayed garbled.  ADOBE Reader was NOT automatically used to open the PDF file!
(5) As a test, I uploaded the webpage and the PDF file to an external server and, again, I used Firefox to retrieve the webpage and to open the PDF file (from the link in the webpage).  It works fine!  Adobe Reader was automatically used to open the file.
(6) As another test,  I opened the webpage in my computer -but using Internet Explorer- and I retrieved the PDF file (from the link in the webpage).  It works fine!  Adobe Reader was automatically used to open the file.

What the heck is wrong?

Thank you!

Dr. TI WOULD wager it was SOMETHING SIMPLE but easily missed like you uploaded the file with a misspelled filename or extension.  The same potentially goes with the link itself.  Check again to make sure it is trying to open a .pdf and not something like a filepdf.txt, or file.pdf' or some other miscellaneous typo.

-Mal