I just realized this question is still open, and maybe I can help with the "long-term archiving" issue. There's a little snippet in the link below about "standard formats to extend the life cycle of the document over time." The idea is that if you use a non-standard format, so many other changes are made over time that the document may not be displayed in its original format by future software versions or operating system updates (e.g. a font pack that is revised or disappears). An archived format embeds all that information instead of linking it. It will also embed other file types, like audio files, that would be managed by the OS. However, if you use a standardized (by ISO or another organization) format, in this case PDF/A, it's likely to be able to be read by many programs and OSs for a long time, as the standards are more "basic/clean," and companies that want to be ISO-compliant will follow them. It's like books that have appendices in them, in which case no matter what changes in the world, you can always see exactly what they were referencing.
https://www.edicomgroup.com/solutions/long-term-electronic-a...