Hi,
There are several user profiles you can use with different permissions.
What you are looking for is probably something in between the "Operator" and "User" profile.
You might probably want to take a look at the specific permissions for those profiles and decide which of them suits your needs or create a new profile with a custom set of permissions.
Anyway I'm not completely sure that a 100% "read only" profile can be created.
Regards
Juanjo