The ornamental design for a printer, as shown and described.
FIG. 1 is a perspective view of a printer;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a right-side elevation view thereof, the left-side elevation view being a mirror image thereof;
FIG. 5 is a rear elevation view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken lines immediately adjacent the claim and that border unshaded regions depict the bounds of the claim and are not included in the claim. All other broken lines are directed to environment. The broken lines form no part of the claimed design.