The ornamental design for a printer, as shown and described.
FIG. 1 is a perspective view of a printer, showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a right-side elevation view thereof;
FIG. 5 is a left-side elevation view thereof;
FIG. 6 is a rear elevation view thereof; and,
FIG. 7 is bottom plan view thereof.
The broken lines depict environmental subject matter only and form no part of the claimed design. The dot-dash lines represent a boundary between claimed and unclaimed subject matter, and form no part of the claimed design.