The ideal scene I have in mind is using a tablet PC in full screen mode, eg. displaying a PDF presentation or a web page design, and some meeting attendant draws his/her ideas/changes/notes on the display, marking areas, writing notes right in place, etc. A piece of software that is (graphically) on top of the display actual in sight to the observer, i.e. has the focus, collects all those “screen touches” and assigns them to the open file. But this should also work with just a normal PC/mouse set up or any tough screen environment. The hard bit would be, so I reckon, for the software to assign some “notes capture” to a certain page of an open document been presented, a subset of the document that is. The two ad hoc solutions that come to mind include either a support for the overlay software by the presenting software, so the assignment is actually done by the presenter. Or else the overlay software hast to have an understanding of all possible file formats’ structures, i.e. PDF, bitmaps, just anything that should be marked. Now, if this file is opened the next time, and the overlay software is activated, it should from it’s database display all notes associated with this document’s page.