Separate naming for invoice and proforma invoice PDFs
When sending and Invoice email, one would benefit from separate naming schemes for proforma invoices and invoices.
Separate document naming whether certain invoice does not have invoicenum assigned (it is a proforma invoice) or invoicenum is already nonempty (a real invoice).
In language files this could be implemented somewhat like this:
$_LANG['invoicefilename'] = "Invoice-";
$_LANG['proformainvoicefilename'] = "ProformaInvoice-";
What do you think? It seems fairly trivial change to me :)