Three options may be set in the pcl5 driver. The driver actually uses HPGL-2 but there is a name conflict among the terminal devices.
Syntax:
set terminal pcl5 {<mode>} {<font>} {<fontsize>}
where <mode> is landscape, or portrait, <font> is stick, univers, or cg_times, and fontsize is the size in points.
set terminal pcl5 landscape