I’m not sure whether there is an easy way to do this, but you can achieve this with user groups and document groups.
Setup a new user groups and document group. Assign the user group to the document group. And set the document group to contain the specific document that you want the user in user group to be able to edit them. Then set the user into the newly created user group that you just made. Now set a user role, so that the user doesn’t have access into the advanced manager area and assign it to that specfic user.
That’s all folks...
Hope I answered what you’ve requested. For more information about this, you can actually read the documentation. It’s easy to read and full of graphic to explain it in more detailed
Btw, I like this approach, so that I can add another documents or users later to this user group and document group. The best thing is, the user on the user group, if you granted them the ability to create a new docs, the new doc will be automatically assigned to the document group.
Hope that helps.
Sincerely,
Wendy Novianto