The ornamental design for a printer, as shown and described.
FIG. 1 is a top and front side perspective view of a printer showing a new design;
FIG. 2 is a top and back perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The dashed lines in FIG. 1 depicts a piece of paper, an environmental aspect only and forms no part of the claimed design. The dashed lines of FIGS. 2 and 4 are for purposes of illustrations portions of the printer that form no part of the claimed design.