The built-in viewer is used when Portable Document Format (PDF) files are set to Open in Firefox in your Firefox settings for different types of files.
3.4 Troubleshoot problems with the PDF viewerįirefox's built-in PDF viewer allows you to view almost all PDF files found on the web without an external application (exceptions to this are PDF files with a MIME type incorrectly set).2.2 Set Firefox to ask you what to do with PDF files.2.1 Disable the built-in PDF viewer and use another viewer.2 Choose another PDF viewer to use by default or set Firefox to always ask.1.1 Use a different PDF viewer for downloaded PDF files.
