When you click on a link to a PDF file or open it from the Firefox Downloads panel, it will be rendered with the built-in pdf viewer. This built-in PDF viewer is enabled by default. 4.4 Troubleshoot problems with the PDF viewerįirefox includes a built-in PDF viewer that 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).3 Set Firefox to ask you what to do with PDF files.2 Disable the built-in PDF viewer and use another viewer.1.1 Use a third-party PDF viewer for downloaded PDF files.
