Foxit Reader

You want to view PDF files but hate Acrobat Reader 'cause it's big, slow, waste memory and need to install. You have another choice, please use Foxit Reader. It's small (over 1MB), fast, don't eat too much memory and don't need to install. Also its UI really looks like Acrobat Reader so you don't need too much time to learn to use it.

Try it and like it!