Adobe Reader has been the dominant PDF viewer for many years, mainly due to the format being so locked down, that Adobe were the only ones able to render it. However that changes ages ago, and now the Internet is full of alternative PDF readers, many far smaller, cleaner, and better then the bloat-ware that is Adobe Reader.
Foxit is probably the second most popular. It comes in a free and enterprise version, plus versions for Linux. Watch out for the sly attempt to add some toolbars and other crap during installation, but once up and running, it does indeed live up to its ‘fast, small, feature-rich’ blurb. It has an amazing ability to constantly consume the same amount of resources for files much larger then its own footprint, and also integrates nicely with all the popular browsers of this half decade.
So if you’re still running Adobe Reader, I would advise giving something new a try, and I hope you’ll find it a pleasant experience - http://www.foxitsoftware.com/Secure_PDF_Reader/.