US Patent 7209948 Collaborative review of distributed content

Collaboratively reviewing a digital document in a computing environment having a visual interface involves first presenting multiple users with a copy of the digital document in a visual interface. Annotations (such as highlights, underlines, or textual annotations) are made by the users and separately recorded, independently of the client application used to view the digital document. The annotations, though, are logically linked to the digital document, and annotations made by a particular user can be recorded over multiple overlays.