Print JS code doesn't work

I created a form with a button that runs a javascript to print the document (is there an easier way to do this in Acrobat (not LiveCycle)??).
I read the scripting guide and added the following code to the button's Javascript:
// get the printParams object of the default printer
var pp = this.getPrintParams();
// set some properties
pp.interactive = pp.constants.interactionLevel.full;
pp.colorOverride = pp.colorOverrides.auto;
// print
this.print(pp);

But the button doesn't work.
What am I missing?

Thanks,

FayeC