%!

% this draws a square of side 1 inch, centred on an 8.5 x 11 inch page

% scale to inches
72 dup scale
% move the origin to page centre
4.25 5.5 translate
% reset the line width to one Adobe point
% by default it is 1 current unit 
1 72 div setlinewidth

newpath
-0.5 -0.5 moveto
  0.5 -0.5 lineto
  0.5   0.5 lineto
-0.5  0.5 lineto
closepath
stroke