You might already know that Firefox can display PDFs from the web, but it can also view files saved on your computer. If Firefox does not appear as an option when opening a PDF on your computer you can use the keyboard shortcut Ctrl+O (or Command+O on Mac) to browse for a file. If you’re on a Mac or have the menu bar enabled on Windows and Linux, you can do it from File > Open File.
Firefox’s PDF features include a sidebar with outline and thumbnail options, a page selector, several zoom options, a full-screen presentation mode, and multiple ways to scroll through pages. You can see all the options by toggling the sidebar (top-left button) and opening the tools menu (top-right button). You can even type and draw on top of PDFs, and save the changes back to a new file.