The ornamental design for printer, as shown and described.
FIG. 1 is a perspective view of a printer showing my new design;
FIG. 2 is a front view of the printer;
FIG. 3 is a rear view of the printer;
FIG. 4 is a right view of the printer;
FIG. 5 is a left view of the printer;
FIG. 6 is a plan view of the printer; and,
FIG. 7 is a bottom view of the printer.
The part represented by the solid line is the part that is being applied for a design registration as a partial design. The broken lines shown in the drawings represent portions of the printer that form no part of the claimed design.