If you want to draw an overlay you should always be prepared for the page to be redrawn. This can happen at any time (sometimes partially). Obvious reasons include navigation, window resizing, dialogs or windows on top; but Acrobat or Windows can also decide to redraw at whim.
What is the difficulty in registering for AVPageViewDidDraw? It is like other notifications. You could register it only when needed, but mostly it would be done just once, and you would check to see if any work was to be done before starting. Check carefully which document is drawing, too, even if you do not expect any others.