Abstract: A device to be associated to a transfer means, generally a transfer cylinder, of an offset type printing machine including more than two units interconnected in series by said transfer means, the device performing the overturning of sheets for printing the sheet on both faces thereof, said device being completely external of said transfer means and including an auxiliary overturning cylinder provided with gripper means for fully detaching and winding thereabout sheets from said transfer cylinder, and a reversal and progressing mechanism adapted to engage the formerly trailing edge of the sheet wound about said cylinder and to said sheet, in the direction opposite to that in which it has been wound, to the or to one of the transfer means for positioning the other face of the sheet for printing thereon in the downstream unit or units.