Lookup Doc.spawnPageFromTemplate() (http://livedocs.adobe.com/acrobat_sdk/11/Acrobat11_HTMLHelp/JS_API_AcroJS.89.542.html) and check the quick bar at the top:
The "F" in the fourth column indicates that you need form rights to use this command. You cannot assign form rights with Adobe Acrobat, you can only do this with LC Reader Extensions. Reader XI gives your form a subset of these form rights so that you can use this command. You do need extended Reader rights to use this command, but you are getting them for free with Reader XI. As I explained, when your form comes with a different set of rights, the rights that travel with the form take precedence, and what you get for free with a non-extended form goes away with your reader extended form.
This is my interpretation, based on what I've read and my experiments.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com