Coming to features offered in this Built-in PDF Reader are
- View PDFs
- Black UI makes you feel part of Firefox
- Zoom in/out contents in PDF file
- Download copy of PDF file you’re viewing
- Navigate between previous and next pages with controls on toolbar at the top,
- Use Toggle Sidebar button on toolbar to access controls for show thumbnails and show document outline
- This PDF Viewer doesn’t interfere with Adobe reader or other third party PDF plugin in browser means when user tries to open any PDF file via link in a page, it will still be loaded by third-party PDF plugin in browser not native PDF viewer in Firefox.
- Still in development not ready for prime time
- May not render some PDF files properly then you need to install third-party PDF reader like Adobe Reader on your Computer
- Lacks print button/support.
To disable native PDF Viewer in Firefox
1. Visit about:config in your browser and proceed by agreeing to the warning
2. Find “pdfjs.disabled” preference and set its value to True.
3. To enable it again set its value to false.
Update: Now for Adobe Acrobat or other PDF Reader Plugin to open PDFs inline in browser, open Firefox options window>Applications tab> for application/pdf choose action as “use Adobe Acrobat” or the plugin name which showed there and click OK to save the changes.