Did you know: You can read PDF files without downloading any addons or plugins on the new Firefox 15.
The above fact is slightly flawed though. Let me explain. Even if you have downloaded Firefox 15 on your computer, you won’t be able to read or view PDF files and documents because, for reason unknown, Mozilla decided to disable PDF reading by default.
This means you won’t be able to open PDF files as soon as you download the new Firefox browser. But the good news? We have a solution.
Launch the Mozilla Firefox browser and type “about:config” (without quotes) in the address bar.
You will receive a warning message. Go ahead and click “I’ll be careful, I promise!”
Type “pdfjs.disabled” (without quotes) in the search box.
Double click on pdfjs.disabled. By double-clicking, we are changing the value from True to False (which means we are requesting to enable PDF reader).
Restart Firefox. Now you should be able to open any .PDF extension files right on your browser.