Yes, there are some available <a href="http://www.rasteredge.com/how-to/vb-net-imaging/image-annotating/">annotation add-on</a> resource, with which you can simply and quicly add and draw annotation object in any shape on image or document page with the annotation position adjustable. And the annotation object can be ellipse, rectangle, rubber stamp, free hand line, etc.
I do not know too much about Alfresco, i have installed alfresco community 5.0 d recently and trying to add a good image annotation addon. Can you further help or guide how can i use rasteredge with alfresco community? or link to similar installation guide will be too helpful.