Abstract: An apparatus is disclosed for packaging large stacks of sheet material such as reams (10) of folio-sized paper. The reams are positioned on a precut bottom carton blank (24) and conveyed to a folding station (110). A top carton blank (50) is then positioned on the upper surface of the ream. Then peripheral flaps (34, 36, 42, 44, 46, 48) on the bottom carton blank are folded upward adjacent the sides of the ream. The preglued side flaps (58, 60) and end flaps (70, 72) of the top carton blank are folded downward into contact with the flaps of the bottom carton blank. All folding operations are performed as the ream moves along an essentially straight path through the apparatus, thus providing a compact packaging system.