The first two options are self-explanatory, while the 'view as HTML' feature works a bit like Google's version of the feature, speeding load times while largely abandoning formatting. This simple little extension gives you complete control over PDF files in a Toolbar button.Rather than stick you all alone with a browser-jarring PDF file, the PDF Download extension provides you the option to: download the file locally, open it with Firefox using the PDF download options settings, view the PDF as an HTML file in the browser, bypass PDF Download, or cancel the link. The problem with opening PDF files in Firefox is that it tends to slow down your performance, especially if you open several of them.