wrinkled, folded, or damaged
wavy at the ends
curled
absorbent
dry and conducive to static buildup
already printed on (such as the back of pre-printed paper)
pre-printed (unless specified)
heat sensitive/non-carbon
too thick or thin
pre-stitched
glued or tacked
stapled or clipped together
dark in places
irregular in length and proportion
Even if compatible paper types are used, print quality may be lower than usual or paper jams may occur if the paper was improperly stored.