restrict acces only to admin account and disable registration and edit function for guests
I have committed some access handling admin functionality. I am not sure about disabling registration because you could still register to monitor changes. This I will leave open to discussion.
With the committed change, an admin user can edit all pages so if you lock all pages, effectively, admin accounts would be the only ones able to edit.
With all pages locked, if I am logged in as admin I don't seem to be able to add new pages.
@kowallek, change has been committed. Or you could just unlock the node you are adding to, add the new page and lock the node again.