You might like to give PDf Xchange from Tracker a go
http://www.tracker-software.com/prod...xchange-viewer
The FREE version of the PDF-XChange Viewer may be used without limitation for Private, Commercial, Government and all uses, provided it is not -: incorporated or distributed for profit/commercial gain with other software or media distribution of any type - without first gaining permission. Software Developers SDK available for licensing in 3rd party software products etc
Free version does support the commenting you are looking for.