The ornamental design for a printer, as shown and described.
FIG. 1 is a perspective view of a printer, as viewed from the front, top, and right side, embodying our design;
FIG. 2 is a perspective view thereof, as viewed from the rear, top, and left side;
FIG. 3 is a front of thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines represent unclaimed subject matter, or unclaimed depth (in the case of dotted lines within solid outlines), and form no part of the claimed design.