I need a system that: A) Let's me and other users add annotations to a document. B) Allows me to view all the annotations added to a doc. C) Automatically, o

I need a system that: A) Let's me and other users add annotations to a document. B) Allows me to view all the annotations added to a doc. C) Automatically, or semi-automatically merges annotations from the "version 1.0" doc into the newly released document for "version 1.1". PDF covers (A) and (B) but I haven't been able to find a tool that does (C).