Depends on what kind of access you want, and where.
* For edit access to public profiles (born before 1880 or manually set as public) you invite as a collaborator
* For edit and merge access for your private profiles, including living you invite as extended family group.
* For view-only access to your private profiles you invite as a friend.
To just view the tree and details of public profiles you don't have to do anything.
If someone have problems viewing historical profiles because they are still marked as private and/or zombies (still living) it is better to use contact manager option and ask him/her to fix the problem since it affects all users.
