You can send a billing document by email if one contact associated with the account to which the billing document relates contains a valid email address and the Billing Contact checkbox is selected on that contact. For more information, see Setting up Document Email.
To email a billing document using the enhanced Billing Document Detail page:
Click Email on the detail page of the billing document you want to send.
Select the recipient of the email.
Click Send.
Salesforce
To email a billing document using the Salesforce Billing Document Detail page:
Click Email PDF on the detail page of the billing document you want to send.
[Optional] To preview the billing document before sending it, click Preview Billing Document.