What you're talking about is a failure in the "addressability" section of the digital media rubric. It's not page-based layouts that make this easy. That's entirely orthogonal. (This new Pageless feature of Google Docs, for example, doesn't make it any better or worse at satisfying the use case you're referring to than it was before.)

I’m thinking specifically as using PDFs as an archival format to snapshot the state of a document at a moment in time. PDFs are inherently page-based (well, at least in the way they are commonly used in business, I know they could be any dimension, but that’s still a “page”).

It isn’t just the ability to have temporal addressability (if I’m using the word the same way as you). I don’t really care if I can time machine back to see how a notion document looked two weeks ago. I need the ability to archive that document, save it outside of notion, send it to my client, etc. You can do this with many different formats, and could also export JSON objects if necessary.

However, when it comes to mixing layout and data, PDF is a pretty good format that has good existing tooling.

So, it’s not entirely orthogonal… it’s not just about recording state in time. You have to be able to share it in a meaningful format — independent of the original application.

Your comment sent me off on a mental tangent for a minute about what it would take to create a PCF - portable canvas format

I suddenly realised I was reinventing HTML!

Just allow people to export HTML/CSS for archival.

A full single-file archival HTML file would really get you pretty far in the regard (embedded CSS, no JS, data/base64 images). You might even convince me that JS is okay if needed to render the page, but a static dom would be better.

All the things you said about PDF are true. You can say other true things, like that it's true that PDF gives these nice archival properties and that at the same time it's true that PDF begins with the letter P. Nevertheless, it doesn't make sense to conclude that what you want from an archive format is for it to begin with the letter P. That PDF simulates physical pages (versus not) is similarly beside the point.