A form can be automatically emailed upon form submission through Form Actions. 

You can manually send a PDF through the Web Portal > Forms > Submitted Forms > PDF > Email PDF on the left of the screen, the contact will auto populate if the form has used the CRM element > you can choose an existing email template or just free text the email content > Send Email. 

This can also be done through a form in the Activity section of the contact card. Web Portal > CRM > Contact > Activity > Forms > PDF > EMAIL PDF. 

On the App > Forms > Submitted Forms > swipe left > Email.