So follow given bellow instructions to disable built in PDF viewer in Firefox. This is another easy method to change required settings and stop using Firefox PDF viewer. Second Method to Turn Off Firefox PDF Viewer! If the plugin ' Chrome PDF viewer' is disable then enable it now. Just paste ' chrome://plugins/' on the search bar and press enter. Note: If still not working then make sure that the Chrome PDF viewer is enabled. Once you will disable add-on you can check the default value set to true.

Right click and press Toggle option or simply double click on the to disable it.You can see that the default value of the preference is set to false, it's meant the PDF reader is enabled.Search for pdfjs.disabledby using the search bar at the top.A warning message will appears, confirm it to move on the next step.Type about:config in the Mozilla Firefox address bar and press enter button.It includes editing Firefox's advanced configuration,by using this method you can easily stop Firefox from viewing PDF in browser. This is the easiest and effective manner to disable built in PDF viewer in Mozilla Firefox. First Method to Disable PDF Viewer Firefox! Once you disable built in add-on, you will automatically stop Firefox from opening PDF in browser. In this article two easy and effective methods are discussed which allows you to turn off Firefox PDF viewer Application.

If you are tired using Firefox as default PDF reader program and want to disable built in PDF viewer in Firefox then this post will surely help you out. Two Ways to Disable Built in PDF Viewer in Mozilla Firefox

Fire fox pdf reader