For many years, I was a member of a wonderful writing group where members met weekly, bringing multiple copies of their latest chapters for peer review. We would sit in a coffee shop and take turns with all of the members reading and red-pen critiquing one person's writing. At the end of each reading/critiquing time, we would discuss the piece so that everyone present could benefit from everyone's input. The marked up paper pages would then be returned to the author and the next author's turn would begin.
This was a wonderful system, but as the group grew bigger we had to split off into multiple critique circles, each meeting at different times throughout the week, with a fixed membership of 5-8 authors each. Eventually we had dozens of weekly meetings, supporting hundreds of active writers, each writing 5 or more new pages per week and printing 5-8 copies of those pages to bring to their circle's meeting.
We were helping a lot of amateur writers, but we were consuming a lot of paper in the process. I still have trunks full of cherished red-marked pages of my writing which I can't quite get myself to throw away. As I have moved away from that group and am considering starting a similar group where I now live, I am wondering that there must be a better way to do this.
So here is my question? Is there any ereader or tablet/laptop software which allows reading, editing and critique-markup of private documents shared among a small group of people?"
...and if there is more than one such solution, what are the strengths and weaknesses of each?