SpotNote 

SpotNote is a quick and easy editing and commenting tool that can be used with many programs. SpotNote allows you to make comments and corrections directly ON TOP of the document, so your original document remains unchanged.
post-it sticky notes notes document editing comments annotations corrections custom notes electronic notes change control document review reminders work flow software

zannoTate 

zannoTate is a vector-based image annotation and drawing program that makes it easy to create professional artwork. You can create anything from simple line item annotation to intricate technical drawings. Even embedded your drawings in documents.
annotate drawing ole art embedded