Mechanism for controlling sheet manipulators, including sheet guides, in a perfector press, when the press shall be switched from obverse-obverse to obverse-reverse printing, or vice versa. A first printing cylinder and an adjacent transfer cylinder of the press have linkages pivoted about the respective cylinder axes and swingable, relative to the cylinders, in coordinated and partly overlapping motions. The linkage of the first printing cylinder repositions a sheet guiding plate by crank, link and guide units. It also repositions the sheet gripping mechanism of the first cylinder and, with lost motion, that of the transfer cylinder. Exact positioning of all mechanisms are provided by detent and release means in the transfer cylinder.