PDF/A, or PDF Archive, is an ISO-standard version the PDF format. Adobe introduced PDF in 1993, and the International Organization for Standardization (ISO) took management of PDF as an open standard in 2008. ISO released PDF/A in 2005. PDF/A is designed to be used with PDF files that need to be archived and stored, and still capable of being opened and read in a viewing tool many years into the future. Hence the standards for PDF/A files differ from regular PDF documents. In one example, to be PDF/A compliant, the fonts in a PDF/A file must be embedded in the file itself so that a viewer does not need to try to access fonts stored in a font directory on a local machine. A sample program is provided to demonstrate working with the PDF/A format, PDFAConverter for .NET Core.
Adobe PDF Library can create PDF/A documents that conform to the ZUGFeRD 2.0 document standard from Europe. The ZUGFeRD acronym comes from the German “Zentraler User Guide des Forums elektronische Rechnung Deutschland,” or “Central User Guide of the Forum for Electronic Invoices, Germany.” This free and open European document standard is designed to allow for companies of all sizes and for the public sector to quickly and easily exchange electronic invoices.
Besides replacing printed forms with PDF files, digital signatures and certification are not needed as long as an audit trail is in place that can track the PDF invoice from the sender to the recipient. Also, the PDF invoice documents can be exchanged in whatever way the two parties involved find most practical. They can be transmitted, but that is not required.
ZUGFeRD 2.0 standard invoice documents use the PDF/A-3 standard because this standard allows for another file to be embedded in a PDF/A document as an attached file. The document must include a ZUGFeRD electronic invoice XML file as an attachment; this file contains the same information as the PDF invoice, but in a structured machine-readable format. So the ZUGFeRD PDF/A-3 document can still be used as an archival document and stored indefinitely. But the primary purpose of the ZUGFeRD standard is to allow business and governmental bodies to be able to much more efficiently process payments.
The ZUGFeRDConverter sample program (.NET Core) demonstrates how to work with the ZUGFeRD standard.
With Adobe PDF Library you can select from these PDF/A formats when generating PDF output files:
| PDF/A-1b | Basic conformance with PDF/A archival standards | ||
| PDF/A-1a | Matches PDF/A-1a, but also provides for accessibility for people with disabilities. This allows a person to work with a PDF document while using assistive software, such as viewing tools that can increase screen resolution or read a document out loud. | ||
| PDF/A-2b | Basic conformance with archival standards but revised for later versions of the PDF format. PDF/A-2 includes options for OpenType fonts, layers, attachments (which themselves must be PDF/A compliant) and JPEG 2000 image compression. | ||
| PDF/A-2u | Matches PDF/A-2b but also requires that all text in the document have Unicode mappings. | ||
| PDF/A-3b | Matches PDF/A-2b, except that it is possible to embed any kind of file in the PDF document. With PDF/A-3 a user can save an XML, CSV, CAD, spreadsheet, or other type of file in the PDF document and still conform to PDF/A standards. The file embedded in the PDF/A-3 does not need to be converted to PDF/A itself. | ||
| PDF/A-3u | Matches PDF/A-3b, but also requires that all text in the document have Unicode mapping. |