- Load about:config in the web browser’s address bar.
- Confirm that you will be careful to proceed.
- Use the search at the top to find pdfjs.enableScripting.
- Set the preference to FALSE with a click on the toggle button at the end of the line.
You can test the effect by loading PDF documents that include scripting from a site like PDF Scripting. Just download the sample PDF documents and check them in the native PDF viewer of Firefox to see if the execution is blocked.