to form stacks of printed products such as books , magazines , newspapers , brochures , etc ., a plurality of printed sheets is delivered by a conveying section and assembled thereon into preliminary products , which are then formed into stacks , where the process for collating the printed sheets into preliminary products is controlled as a function of the size of the stack of printed products to be formed . a device for implementing the process includes a collating device for forming preliminary products and an indirectly downstream stacking device connected to a control unit .