That depends on the creation process and the programs involved. Either the source program (eg the invoicing program) that generates the invoice document can already be used directly PDFOutput / A or just PDF, which then follows with a converter after PDF/ A must be transferred. A possible converter would be, for example intarsys PDF/ A Live!. Another option is to use a PDFPrinter driver, the PDF/ A can create. To do this, the invoice from the source program must then be sent to the relevant PDF-Printer to be printed. Well-known solutions are for example PDFCcreator.
