What are some alternatives?
When comparing Sumatra PDF and Cool Reader, you can also consider the following products
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.
FBReader - FBReader is an e-book reader for various platforms. Features:
PDF Reader X - PDF Reader X is a nest in the class PDF reader, PDF annotator and PDF editor for the Mac OS X operating systems.
Amazon Kindle - Amazon Kindle software lets you read ebooks on your Kindle, iPhone, iPad, PC, Mac, BlackBerry, and...
Okular - Okular is a universal document viewer based developed by KDE.
calibre - Ebook manager, viewer & converter