Ask HN: Tool for getting comments on a doc, with each reviewer private?

I'd like to send around a document to people I'd like them to be able to comment inline in the document without them having to sign up for a new service (if it's google docs that's fine because they already would have an account) I'd like people to be able to comment on the doc, without knowing/seeing that other people are also commenting on the same doc When I view the doc, I'd like to see all the comments When they view the doc, I'd like them to see just their comments One way of doing this - manually copying and sharing a new version of the doc for each person Is there some piece of software that does this in a more automated way?