Freezing parameters before delivery to client

Hello everyone!

My question is how can I freeze all or parts of a definition because of the fact that I want to deliver this model or the result of it to the client and don't want to change, or possibility to cjange, any parameters afterwards due to legal concerns. 

I mean I'm gonna have a copy of the model and continue working but just before every delivery I need to show to the client that the parameters in the file are locked. 

Or probably put a password on the file? 

Best practice ? 

Regards

Shahrokh