Lawyers are often amazed at the number of clients who will sign legal documents without getting copies of them. A common scenario occurs when a renter is looking for an apartment and dealing with a real estate broker. Brokers routinely have prospective tenants sign leases and forward them to the landlord for approval. It is not unheard of for a landlord to then change the lease a new tenant signed before returning it. Without a copy of the original, you'll have a hard time proving that the landlord changed the terms of the agreement after you agreed to them. Changes of this type are improper, but are hard to prove or correct. That's true even if you hire an attorney and try to subpoena the original documents, or attempt to establish evidence by cross-examination of the broker in court. It's an expensive proposition. So get and keep copies of whatever you put your signature on.