PdfProcessing: Add support for embedding of ZUGFeRD invoices
ZUGFeRD (acronym for Zentraler User Guide des Forums elektronische Rechnung Deutschland) is a specification for the electronic invoice format of the same name.
However, ZUGFeRD/X-Rechnung is a German standard, there is also an equivalent in France (Factur-X) and both are based on the international UN/CEFACT Standard „Cross Industry Invoice (CII)“ and the ISO standard PDF/A-3. Here is the related law/text by the EU: https://eur-lex.europa.eu/eli/dir/2014/55/oj?locale=en