How do I open an external pdf file with AS3?

I've searched and found this code:

import flash.net.navigateToURL;
import flash.net.URLRequest;

myButton.addEventListener(MouseEvent.CLICK, goPDF);

function goPDF(event:MouseEvent):void {
var url:String = "OAI/InsuranceDiagnosticCodes.pdf";
var request:URLRequest = new URLRequest(url);
navigateToURL(request);
}

but nothing happens when I click on the button.

What am I dong wrong? Btw, I'm relatively new to Flash CS4 and AS3.