What's the most annoying Internet-related application of all time? For many people, that question has a simple answer: Adobe Reader. Countless documents online are in the Acrobat format, so there's no way around it: You need Adobe Reader. But it's bloated and prone to crashes, nobody's idea of a good time.
Foxit Reader is a far better solution. It's small and loads much faster, so it doesn't take up much memory when you use it. It also doesn't seem to suffer from the same instability issues as Adobe Reader does. The program also has some nice extras, such as the ability to embed comments. (However, when you embed comments, the page you mark up will show that you're using an evaluation version of the software. You can pay for the Pro pack to get rid of those marks and get some other extras as well.)
Note that when I installed the program, it integrated directly into Internet Explorer as the default PDF reader, but it didn't similarly integrate into Firefox। To make it the default in Firefox, you'll have to select Tools, Options and then click the Manage button in the File Types area. Double-click each of the files that Adobe Reader opens, and tell Firefox to use Foxit Reader instead.