A printing unit for printing a web of paper is provided. The printing unit includes a frame and an upper printing group and a lower printing group. The printing unit has at least one throw-on configuration and a blanket-changing throw-off configuration. The blanket cylinders are capable of each receiving at least one tubular blanket. The frame has, in at least one lateral wall, at least one opening to allow the passage of the tubular blankets. In the blanket-changing throw-off configuration, the blanket cylinder of the upper printing group has been moved upwards relative to the position which it occupies in the throw-on configuration and the blanket cylinder of the lower printing group has been moved downwards relative to the position which it occupies in the throw-on configuration, so that an adequate space is provided between the blanket cylinders to allow a web of paper printed by another printing unit to pass between them.