The ornamental design for a printer, as shown and described.
FIG. 1 is a front perspective view of a printer showing our new design;
FIG. 2 is another front perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dashed broken lines depict environmental subject matter, are for illustrative purposes only and form no part of the claimed design. The dash-dot-dash broken lines define the bounds of the claim and form no part thereof.