I would like to have external proofreaders to work directly inside my Drupal site. Basically they should be able to create new revisions, annotate, comment etc without affecting what users see without my approval. Particularly the node might already be public.

"Revision Moderation" module sounds a bit like what I want, but it seems not to be so much used, and I run into other modules like "Workflow".

What is important for me:

1. Possibility to work on content already published
2. Easy for the proofreader, easy for me to direct her to the right location
3. Other useful features such as comments (Like those balloons in Word), diffs etc

(I guess I could work around (1) by copying the content)