The HP LaserJet II and HP DeskJet drivers have a single option.
Syntax:
set terminal hpljii {<resolution>}
set terminal hpdj {<resolution>}
where <resolution> is the resolution of the output in dots per inch. It must be 75, 100, 150 or 300. Note: there must be enough memory available to rasterize at the higher resolutions.
Example:
set terminal hpljii 150