Abstract: A strip provided adjacent the edges thereof with perforations is driven forwards during a printing operation by the cooperating printing and counter-pressure cylinders of an offset mechanism, and by two pairs of pin tractors, pins of which enter the somewhat larger perforations. When the cylinders release the strip, same is moved backwards by the pin tractors over a distance equal to the difference between the forward displacement and the length of a form. To position the strip before a new printing operation, those pins going through the perforations of the pin tractors are moved a little forwards until they lie anew frontwards in the perforations.