An automatic pre-printed sheets insertion system integratable into an otherwise conventional printer, without requiring any additional space, yet enabling the feeding of selected pre-printed sheets into the printer output path, bypassing the print engine and fuser, yet integrating collated with the output of regular sheets being regularly fed and printed within the printer. It includes a separate insert sheets feeding system and feeding path for feeding insert sheets from a bi-directional sheet feed tray which can be mounted in the same location as a normal sheet feed tray. The separate path can be through an existing inverter. The special tray can be a dual-mode tray and/or a repositionable tray for feeding blank or other normal sheets in one direction for printing and for feeding insert sheets in the opposite direction to be integrated into the printer output.