Invoicing: Allow types to add text and watermarks (#5453)

src/pretix/base/invoicing/national.py

@@ -22,7 +22,7 @@
 
 from django import forms
 from django.core.validators import RegexValidator
-from django.utils.translation import pgettext_lazy
+from django.utils.translation import pgettext, pgettext_lazy
 from django_countries.fields import Country
 from localflavor.it.forms import ITSocialSecurityNumberField
 
@@ -73,3 +73,12 @@ class ItalianSdITransmissionType(TransmissionType):
         if is_business:
             return base | {"company", "vat_id", "transmission_it_sdi_pec", "transmission_it_sdi_recipient_code"}
         return base | {"transmission_it_sdi_codice_fiscale"}
+
+    def pdf_info_text(self) -> str:
+        # Watermark is not necessary as this is a usual precaution in Italy
+        return pgettext(
+            "italian_invoice",
+            "This PDF document is a visual copy of the invoice and does not constitute an invoice for VAT "
+            "purposes. The invoice is issued in XML format, transmitted in accordance with the procedures and terms "
+            "set forth in No. 89757/2018 of April 30, 2018, issued by the Director of the Revenue Agency."
+        )