HowTo: Firefox Disable Default PDF Viewer / Plugin

To disable the default PDF viewer in Firefox, you can follow these steps:

1. Open Firefox and type about:addons in the address bar and press Enter.
2. In the Add-ons Manager, click on the "Plugins" tab.
3. Find the plugin named "Portable Document Format (PDF)" in the list.
4. Click on the "Never Activate" button to disable the plugin.
5. Restart Firefox for the changes to take effect.

rnThis will prevent Firefox from using its built-in PDF viewer to open PDF files, and instead, PDF files will be opened with the default PDF reader set on your system.

If you prefer to use an alternative PDF viewer as a plugin, you can install it from the Firefox Add-ons website and enable it in the Add-ons Manager.