That depends on the creation process and the programs involved. Either the source program (e.g. the invoicing program) that generates the invoice document can output PDF/A directly or only PDF, which then has to be converted to PDF/A using a converter. A possible converter would be eg intarsys PDF/A Live!. Another possibility is to use a PDF printer driver that can create PDF/A. To do this, the invoice must then be printed from the source program on the relevant PDF printer. Known solutions are eg PDFCreator.
Publicly appointed surveyors can use electronic signatures according to eIDAS regulation use (Leipzig, 26.02.2025) Since the beginning ...