Perfect PDF Reader is the best free alternative tool for viewing PDF documents after adobe reader. But it is actually better than Acrobat Reader as it is very fast as compared to acrobat reader.
Perfect PDF Reader is one of the very lightweight and fast PDF viewer which is free from any heavy menus like adobe acrobat reader.
It provides a cool looking interface around the PDF to be read, you can review all the PDF documents in the same ribbon like interface that appears with Microsoft Office