I've heard that reading glasses (negative number lenses but with a "smaller" prescription) need a smaller PD than distance glasses because the pupils are closer when looking at close objects.
At first glance this seems wrong because the center of a lens should be perpendicular to the center of the retina, not the rotated pupil (or perhaps somewhere in between). Which, if anything, would mean that the PD should be greater. Or perhaps this is a mistaken assumption? I'm assuming the lenses are not rotated on reading glasses.
So to conclude, do reading glasses need a smaller PD?
New "bumped to the homepage by Community♦" edit
By reducing the PD we are not only aligning the center of the lens with the line of sight (which, generally, is good). We are also de-aligning (skewing?) the "center" around which the lens is made (which is where the eye is supposed to be) from where the eye is (which is bad).
Any answer needs to address that. Perhaps by saying it's negligible, or that it's better not to change the PD..., some answer.