Italian law requires invoices to have a progressive number. For this I set up the billing with the writing WEB-[[number]].
This writing does not appear in the invoices. The PDF contains the invoice key but not this data. (see screenshots)
How can I edit the PDF of the invoice to also write the dialed number as set?
I think the file to edit is components/com_payplans/themes/wireframe/invoice/pdf_content.php but which variable contains "WEB-123"?
Is there a way to make this change and make it valid even after periodic PayPlan updates without being overwritten?