PDF reader that also lets me make comments

[Leros]

I'm reading a lot of research papers (which are usually PDFs) and it would be nice to make notes along the side as I read.

Does any PDF software (preferably free) do this?

 

[RavenSEAL]

Foxit reader? Not sure if i lets you comment, but its so far the best FREE PDF reader in the market.

http://www.foxitsoftware.com/pdf/reader/

EDIT: Ok, it actually does, check the right corner of the toolbar, look for the chat box.