EPC-Document

Hi,

I've just started using ARIS for Business Process Modeling and I have a problem with EPC model: ARIS won't let me connect a Document Object with an Event or a Process Interface, which is a problem for me.

Is there a method to overcome this odd?Is it just a matter of setting for the Document Object itself? if so, where can I modify that? Have I to modify settings of the entire model? how?

Thank you for your help!