var doc = app.activeDocument; 
 
var ph = _round(doc.documentPreferences.pageHeight, 100); 
var pw = _round(doc.documentPreferences.pageWidth, 100); 
 
function _round (val, fac) { 
	return Math.round(val * fac)/fac; 
} 
 
alert(ph + " x " + pw); 

var doc = app.activeDocument; 
 
var pb =  doc.pages.item(0).bounds; 
var ph = _round(pb[2]-pb[0], 100); 
var pw = _round(pb[3]-pb[1], 100); 
 
function _round (val, fac) { 
	return Math.round(val * fac)/fac; 
} 
 
alert(ph + " x " + pw);