"3. PDF Download - convert web pages to PDF
PDF Download is a nice, feature-rich add-on which will convert a
web page to PDF on demand and it will save it on your hard drive.
When you will select this action it will also open a new tab (or
window, depending on the settings) with the homepage of PDF
Download. This add-on also offers the possibility to specify the
format of the PDF (portrait or landscape) and how to handle
margins."