Stage.scaleMode = "noScale";
var theWidth = Stage.width;
var theHeight = Stage.height
PFbackground._width = theWidth;
PFbackground._height = theHeight;

var resizeListener:Object = new Object();
Stage.addListener(resizeListener);

resizeListener.onResize = function () {
    PFbackground._width = Stage.width;
    PFbackground._height = Stage.height;
};