How can I create a PDF/A-3 in ERPNext?

Part 3 of the standard, published on October 15, 2012
Differs from PDF/A-2 in only one regard: it allows embedding of arbitrary file formats (such as XML, CSV, CAD, word-processing documents, spreadsheet documents, and others) into PDF/A conforming documents.

I ask for this type of document, because it’s the basis for eInvoicing - not editable invoices. PDF/A is an international standard defining the use of the Portable Document Format (PDF) for archiving documents.

Thanks for your support.