Foxit Reader is a free and light-weight multi-platform PDF document viewer. Its core function is compatible with PDF Standard 1.7.
Whether you're a consumer, business, government agency, or educational organization, you need to read, create, sign, and annotate (comment on) PDF documents and fill out PDF forms. Foxit Reader is a small, lightning fast, and feature rich PDF viewer which allows you to open, view, sign, and print any PDF file. Foxit Reader is the only high volume PDF reader providing a complete PDF creation solution, providing the power of PDF creation to every desktop. Foxit Reader comes equipped with comprehensive protection against security vulnerabilities, keeping your system and company safe.... More Info »
Available also as portable app: http://portableapps.com/apps/office/foxit_reader_portable