This is seen when downloading in PDF version, making use of the option that has the system. This is correct
What it follows is that the error is given when sending the mail, attach an incorrect version of the PDF.
I have a case, where a company still can not generate invoices, just vouchers. And everything works well when using this option, the only thing is that by sending the PDF by email, the payment word is changed to invoice, and that hurts us a lot legally.