Printing puzzle

[David Epstein]

The question:  how can I find out, by script, how big the unprintable  
margins are when the Page Setup dialog has been set to some scale  
other than 100%?

At 100%, there's no problem.  For example, the unprintable right  
margin = item 2 of the printPaperSize - item 4 of the printRectangle.

But at any other scale I can't use this calculation, because while  
the "printRectangle" responds to a Page Setup choice of scale, the  
"printPaperSize" does not.

Thus if I set the scale to 50%, the printRectangle of 36,36,1188,1504  
tells me the pixels I can fit into a letter size page after shrinking  
them by half and avoiding the unprintable margins.  This means the  
left unprintable margin on the printed output will be 18/72 of an  
inch (shrinking the 36 by 50%).  But I do not see any way of learning  
this information in a script, because the 50% scaling factor is not  
being reported, and the printPaperSize doesn't change the way the  
printRectangle does when the scale changes.  (The "printScale" seems  
to return 1 regardless of what I do to the Page Setup dialog).

What I'm trying to do is show on the screen is both a rectangle that  
will, when printed, be 1 inch from each edge of the paper; and also  
as much space outside of that rectangle as can be printed to.  Thus I  
need to know how much of that 1 inch cannot be printed to.

Many thanks for any suggestions.

David Epstein