Submitting only the XML data is the default. If you want to submit the completed PDF instead of just the XML data, then you need to set up your submit button to do so. When you use the "e-mail submit" button or the "http submit" button from the standard library, you can't do that. Instead, add a regular button. On its Field tab, set the "control type" to "submit". An additional tab called submit will appear. On the submit tab, set "submit as" to "PDF". Now, in "Submit to URL", enter mailto:whatever@whatever.com.
For this to work, your users will need Adobe Acrobat. Well, maybe not. If your users only have the free Reader it should be possible if you add usage rights to the form, but I haven't tried that.
Hope this helps.
Jared Langdon
http://www.jlangdon.ca