Described herein is a print medium support mechanism for supporting a print medium such as paper in a print zone adjacent a printer's printhead. The print medium support mechanism includes at least one drive roller positioned upstream from the print zone of the printer to feed paper into the print zone. An upper print media guide is positioned adjacent the drive roller between the drive roller and the print zone to contact and support the paper from above. A lower print media guide is mounted downstream from the upper print media guide to pivot between retracted and non-retracted positions relative to the print zone. When in its non-retracted position, the lower print media guide contacts and supports the paper from below. The support of the upper and lower print media guides against opposite sides of the paper is primarily responsible for establishing the shape and angle of the paper as it passes through the print zone. The print medium support mechanism includes a pivot stop which is adjustable to set the vertical position of the lower print media guide relative to the upper print media guide when the lower print media guide is pivoted to its non-retracted position. This effectively establishes a desired print medium shape and angle. A separate media-to-printhead spacing adjustment mechanism is provided for adjusting the vertical positioning of the printer's printhead relative to the paper. Because of this, the media-to-printhead spacing can be set without affecting the settings made to obtain the optimal print medium shape and angle.