Abstract: A paper cutter or trimming device comprises a cutting board including measuring indicia, a rail assembly, and a carriage assembly including a circular blade. The indicia are calibrated in a scale measured from a predetermined cut line. The rail assembly is mounted in a perpendicular relation to the measuring indicia for pivotal movement between operative and inoperative positions with respect to the cutting board. The carriage assembly is mounted for sliding movement on the rail assembly. The cutting board may include a positive stop, and the rail assembly may be biased against the at least one stop when the rail assembly moves to the operative position.