The policy in some companies is that when the aircraft moves by its own power, the Captain automatically accepts the ACARS loadsheet, thereby "signing" it by accepting to fly with the load as indicated on the ACARS loadsheet.
However it is advisable to get a copy of the full format loadsheet as at some less sophisticated stations (destinations/not home base) it makes it easier to dechipher the details in case you have to do your own loadsheet for the return flight and/or to assist the handling agent.