PDF Download is a Firefox extension that improve your surfing experience: when you click on a link to a PDF file, it allows to choose if you want to view the PDF file inside the browser (as PDF or as HTML), outside Firefox or if you want to download it.
OpenPGP...in your browser.
Encrypt, decrypt, sign, verify, manage. The Firefox Add-on for OpenPGP management. FireOPGP is a branch replacement for FireGPG. It uses the OpenPGP standard and requires the GnuPG software.