Email confirmation is not part of the SMTP, Simple Mail Transfer Protocol, that all email clients use. Also not all email clients support generating a receipt upon an email sent with this option.
The more consistent and reliable method is to submit the form data to a web service that will update a data base or email the final recipient and that could also email a confirmation including the completed PDF form.
Email is not considered secure and except for very non-sensative personal data should not be used for the submission of completed forms.