Shared page-document permissions

Hello All,

I have a client that would like to be able to have two people be able to access and edit a page or pages.

One of the people would have access to multiple persons pages and the other persons would have no access to each others pages.

I looked at BuddyPress Docs to do this but it does not support this granular type of page security.

Also looked at WP Revisions and SP Project but they have the same limitations…

Anyone done anything like this?