A printing unit for influencing lateral web spreading in particular in rotary presses, which makes constant contact conditions possible across the width in the rubber-rubber nip and improves the lateral-register quality and the web run without using concave or convex blanket cylinders, has a blanket cylinder and plate cylinders which can be set against the former for printing on one or both sides of a web. The web passes through between the blanket cylinders in a contact zone, it either being possible to skew at least one of the blanket cylinders with respect to the respective plate cylinder or it being possible to skew at least one of the plate cylinders with respect to the respective blanket cylinder, for producing a concave velocity profile on the web.