Terms and conditions

I looking for a solution for my costumers instances.
I need an app or any other solution for my costumers required to accept terms and conditions before use the cloud, and after them accept send to me a signed copy off them.

I see in other post how change the first run wizard, but I don’t want to change anything, because after this it’s not possible to update and also I don’t have any copy of the accepted terms.

Any idea??
Thanks for all