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