PDF forms can email data filled on the PDF form fields by emailing it as a FDF file.  

The reason the data has to be emailed as FDF instead of PDF is that PDF editing/saveing requires a PDF Professional Program however reading a PDF can be done using a free PDF Reader program such as Adobe Reader.

After the PDF is filled out, there will be a Email button on the form that can trigger the form data to be emailed as a .FDF file attachment.  The user will choose to Email it through there Desktop Email App such as Outlook or Save to send through webmail such as Yahoo.

The original owner of the PDF will recieve the FDF file in their email inbox.  When opening the FDF file it will ask the owner to browse/choose the original PDF file.  Then it will open the PDF and populate the proper fields using the data from the FDF file.