warningFactur-X / ZUGFeRD containercontainerPDF
The XMP metadata must contain the Factur-X or ZUGFeRD extension schema.
XMP metadata is present but contains no Factur-X or ZUGFeRD extension schema.
Add the fx: schema (urn:factur-x:pdfa:CrossIndustryDocument:invoice:1p0#) with DocumentType INVOICE, DocumentFileName, Version and ConformanceLevel.
Nothing is stored, and the whole invoice is checked, not just this rule. A PDF only works if it is Factur-X / ZUGFeRD — a PDF with the invoice XML inside it.