You can send invoices and bills to your guests directly from the Invoices module. They will be sent in the form of an email with the sales document attached.
1. Open an invoice or Issuing an invoice.
2. Click Send.
3. Enter the guest's email address.
4. Verify the Subject and Body of the message.
5. Mark Attach PDF.
6. Send the message.
Your invoice email has been sent to a visitor.
If you want to change the look of the message template, go to the article: Invoice email template.