How to Enable the Built-In PDF Viewer in Firefox

Firefox 15 introduced a new feature, though disabled by default, that allows you to view PDF’s from directly within a Firefox tab. This tutorial will show you how to enable this feature, so that you don’t have to use the Adobe Acrobat Add-on to accomplish the same thing.

I’ve never loved having to use the Adobe Acrobat Add-on to view PDF files in Firefox. Fortunately, the Firefox developers have been working on their own PDF viewer for Firefox. This brief tutorial will show you how to enable it.

1. In the Firefox Address Bar, type about:config (without http:// or anything else) and hit enter.
2. If prompted, click the I’ll be careful, I promise! button.
3. In the Search: field, enter in pdfjs.disabled
4. You should see only one entry (the pdfjs.disabled one) in the Preference Name section.
5. Double-click it to change the Value to false
6. Now restart Firefox. Once Firefox has opened again, click the “Firefox button” (top left corner of the browser, see image below) and select Add-ons
7. Locate Adobe Acrobat in the Add-ons Manager and click the Disable button.
8. Now when you click on a link to a PDF file while you’re browsing, the PDF will open inside of the Firefox window, using Firefox’s built in PDF viewer. There are a number of features available using this viewer – you can increase and decrease the size of the font in the PDF, add or remove the ‘sidebar’, jump to specific pages etc.


click to enlarge

9. Now you don’t have to slow down Firefox with Acrobat! :)