Foxit Reader is a good Adobe Reader alternative which also is small in size. It's very good at viewing PDF files on your pc and is quick and responsive for that purpose.

However if you prefer viewing PDF files online then there are better alternatives mainly PDF-XChange Viewer. The problem with using Foxit Reader in the browser is it is known to cause browsers to freeze or crash while waiting for the PDF file to download onto the browser screen.

I myself prefer viewing PDF files in my browser over having to download them first and in such I believe PDF-XChange Viewer is a better option seeing as it can do everything Foxit Reader can do but without causing your browser to crash or freeze when viewing PDF Files inside the browser.