We provide a tool in our application just for this need. Our "Lock Drawing" function turns the entire drawing into a MINSERT. About the only thing the reviewer can do is Erase the Minsert... can't Move, Copy, or otherwise edit any entity in the drawing. Of course a decent programmer could write a Deminsert routine, but most people reviewing a drawing don't have that skill... most don't even know what a Minsert is. Haven't tested this since ACAD 2006, so I don't know whether ACAD has changed the definition or limitations of Minserts.