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 left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a rear 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 and form no part of the claimed design. The dash-dot-dash broken lines define bounds of the claim and form no part thereof.