Foxit (PDF) Reader
Manufacturer: Download site
Price: free / OS: Windows and Linux
Without qualification, the best of the PDF readers is without question, Foxit Reader free edition. There are no ads. You may select to add a browser tool bar if you like. The environment Foxit presents is just spectacular. It is fast has a small footprint and integrates seamless with your browser.
Suggestion, download and install the exe and not the Firefox addon.