Unable to add items to dropdown list using javascript

Hi,

I'm trying to add additional items to a dropdown list at runtime using javascript.

I'm doing this by invoking the addItem method on the dropdown list field during its initialize event.

However when I run the generated pdf in Acrobat Pro, I get the following error in the console -

GeneralError: Operation failed.

XFAObject.addItem:3:XFA:form1[0]:#subform[0]:field0[0]:initialize

Method: 'addItem' cannot be called because doing so would violate this document's permissions settings.

The pdf form has no signatures or any other stuff in it.

What additional permissions do I need to add and how ?

You can view the pdf here -

https://dl.dropboxusercontent.com/u/8022836/xfa3_test.pdf

Thanks,

Joel