Poser is based upon OBJ files which have no real world coordinate measure definitions.

1 PNU is 1 OBJ nothing more, nothing less.

Once upon a time, in Poser 4 manual there was a one-liner hint that P4 male was "about 6 feet high" (high, not tall, because it is just a mesh, not a person) and the corresponding mesh had a vertical size of .751 OBJ units so the equivalence 1 PNU == 8 feet.

I personally like to think in terms of 1 OBJ unit == 1 meter (which is also the default when using Blender in metric mode) so there is are 2.44/.41 factors when scaling from Poser/into Poser.

GIMP 2.7.4, Inkscape 0.48, Genetica 3.6 Basic, FilterForge 3 Professional, Blender 2.61, SketchUp 8, PoserPro 2012, Vue 10 Infinite, World Machine 2.3, GeoControl 2