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 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 evenly spaced and dot-dash broken lines immediately adjacent to the shaded areas depict the bounds of the claimed design, while all other broken lines are directed to environment. The broken lines form no part of the claimed design.