Don't use the email submit button ...that is programmed to submit XML. Use a regular button and make it a type Submit. This will activate the Submit tab on the Object palette. You can set the URL as a mailto:emailAdress and in that screen you can also choose the Submit As option ...choose PDF.
You will also have to Reader Extend the form to allow a local save before you can mail a PDF. This can be done in Acrobat under the Advanced/Extend Features in Adobe Reader option.
Paul