This excellent robust tool for reviewing, printing, and marking up design files is FREE. It is expected to be shipping in about a month. On the Beyond the Paper blog by Volker Joseph there is a video posted showing some of the enhancements to the Autodesk Design Review 2010.
There is also a summary list of enhancements in another posting.
One Autodesk Design Review 2010 enhancement people have had questions on is “how do the new digital signatures help security”. That is quite simple, nothing is 100% secure not even paper drawings but digital signatures add one more level of security as well as help the user assure the design has not changed from when the design had the digital signature applied. This is extremely important for archived design documentation for safety and legal responsibilities.