Abstract: An apparatus for printing letters, numerical characters and symbols in response to electronic data transmitted from a host machine onto both surfaces of a sheet of paper or film. Rollers move the sheet material along a path toward an outlet, a first printer prints on one of the surfaces of the sheet material within the path, and a second printer prints on the other surface of the sheet material within the path at a position nearer to the outlet than the first printer. A position detector detects the position of the sheet material within the path, and a controller concurrently and independently processes at least parts of the printing operations by the first and second printers based on the position detected by the position detector.