Clear Cache and Cookies: Sometimes, corrupted cache or cookies can cause issues. Go to the menu > Settings > Privacy & Security > Cookies and Site Data > Clear Data. Select both options and click "Clear."

   Disable Hardware Acceleration: Hardware acceleration can sometimes cause display issues. To disable it, go to the menu > Settings > General > Performance. Uncheck "Use recommended performance settings" and then uncheck "Use hardware acceleration when available."

   Check PDF Viewer Settings: If you have a PDF viewer plugin or extension installed, it might be causing the issue. Try disabling or removing any PDF-related extensions. You can do this by going to the menu > Add-ons and Themes > Extensions.

   Try Safe Mode: Start Firefox in Safe Mode to see if the issue persists. To do this, go to the menu > Help > Restart with Add-ons Disabled. If PDFs work in Safe Mode, the issue may be related to an extension or theme.

   Reset Firefox: If none of the above solutions work, you can try resetting Firefox to its default settings. Go to the menu > Help > More Troubleshooting Information > Refresh Firefox.

   Check for Conflicting Software: Sometimes, other software on your computer (like antivirus or PDF software) can interfere with Firefox. Try temporarily disabling your antivirus or any PDF software to see if that resolves the issue.

   Reinstall Firefox: As a last resort, you can uninstall and then reinstall Firefox. Make sure to back up your bookmarks and settings before doing this.

Update Firefox: Ensure that you are using the latest version of Firefox. Go to the menu (three horizontal lines in the upper right corner) > Help > About Firefox. This will check for updates and install them if available. Clear Cache and Cookies: Sometimes, corrupted cache or cookies can cause issues. Go to the menu > Settings > Privacy & Security > Cookies and Site Data > Clear Data. Select both options and click "Clear." Disable Hardware Acceleration: Hardware acceleration can sometimes cause display issues. To disable it, go to the menu > Settings > General > Performance. Uncheck "Use recommended performance settings" and then uncheck "Use hardware acceleration when available." Check PDF Viewer Settings: If you have a PDF viewer plugin or extension installed, it might be causing the issue. Try disabling or removing any PDF-related extensions. You can do this by going to the menu > Add-ons and Themes > Extensions. Try Safe Mode: Start Firefox in Safe Mode to see if the issue persists. To do this, go to the menu > Help > Restart with Add-ons Disabled. If PDFs work in Safe Mode, the issue may be related to an extension or theme. Reset Firefox: If none of the above solutions work, you can try resetting Firefox to its default settings. Go to the menu > Help > More Troubleshooting Information > Refresh Firefox. Check for Conflicting Software: Sometimes, other software on your computer (like antivirus or PDF software) can interfere with Firefox. Try temporarily disabling your antivirus or any PDF software to see if that resolves the issue. Reinstall Firefox: As a last resort, you can uninstall and then reinstall Firefox. Make sure to back up your bookmarks and settings before doing this.