Embodiments herein comprise an apparatus that includes a printing engine and an interposer adapted to receive printed sheets from the printing engine. The interposer adds insert sheets between printed sheets. The interposer includes a decurler positioned within the interposer so as to decurl the printed sheets after the interposer adds the insert sheets. The printing engine adds a curl to the printed sheets and the decurler removes the curl from the printed sheets. The decurler can comprise a roller-based decurler, a heated decurler, a pressure based decurler, and/or a moisture-vacuum based decurler.