Abstract: A low cost, variable, modular, web-fed offset lithographic printing unit or tower is disclosed which allows significant economies in production and maintenance, and can be easily and quickly modified in the field using interchangeable modules so as to vary printing characteristics. The printing tower, in the straight-through variable perfector form thereof, is preferably provided with a printer module having upper and lower web-printing blanket rollers; in addition, the tower has corresponding upper and lower inker modules for the respective blanket rollers. The upper inker module is mounted for pivotal movement about a horizontal axis so that it can be shifted between a normal inking position over the printer module to a retracted, printer module-clearing position allowing removal and/or replacement of the printer module by essentially vertical shifting of the printer module.