Imagine layed out in front of you is a large board with little white pieces of paper representing the cover pages of system files on them. You are shown a title, and a modification date. How might one indicate that said file contains not only text, but drawings. Specifically, annotations and highlighted sections?
In my current implementation, I show the same white page, but with it's upper right corner colored yellow, which I'm starting to feel doesn't accurately represent that the document contains annotations.
My initial thought would be to put a bookmark image in place of the yellow corner, but I felt that would be overly-confusing and the wrong symbol for a document containing annotations.