"Some time ago there was a tutorial (Dr. Geep) showing how to smooth the sharp edges of a standard square object by exporting it as a wavefront obj. and reimporting it with weld identical vertices checked.
I can't get this to work in Poser6. Any ideas? Thanks. Ken"

It won't work on a square. A square (not the high-res one, the normal single-sided square) is a plane. It has 4 vertices, one at each corner. They can't be smoothed.

What can be (somewhat) smoothed is the cube/box.
The box that Poser supplies is made up of 6 squares, one for each side.
Which means that Poser treats the box as six separate (square) objects. Since it can't "smooth" a square, it can't smooth the box.
This box has 24 vertices. 3 at each corner. (6 sides each with 4 corners, 6 x 4 = 24)
The corners of each side meet exactly. (So there are 3 vertex entries in the mesh data for each corner which have identcal values. Each of those entries is associated with a different side of the box).

By exporting/importing (with "weld identical vertices" checked), those 6 corners with 3 verts each get welded into a new object which has 1 vertex at each corner. Each vertex is shared between the 3 adjoining faces. Now Poser only has a single object, with a total of 8 vertices.

Since the faces are now "joined together", Poser can calculate the angle between one face and another. And can "adjust" it when rendering so as to give the appearance of a smoother join.

You may need to adjust the "smoothing" value for the imported box, either in the rendering options, or in the properties dialogue for the box for the effect to be seen...

I really hope this helps, 'cos it has just scrambled my brain trying to explain it in words...:-))

Cheers,
Diolma