How to protect a project data after finalize it

We want to have visibility of the project once it was finished.   But we need to protect the data to changes.   Do you know any way to do it?   At this time we are changing each user permissions to "read only", but we have projects with more than 100 users, maybe it could be another easy way to do it.

Thanks in advance

I would just change all of the roles on the project to the 'Observer' role.

That would probably be the easiest solution.

Regards

Jim.