Split text across DIN A4 pages

I'm working on creating an editor using DIN A4 pages with specific text formatting using React.

Right now, my content is handled by an editable div (with more divs nested inside it for formatting).

If possible, I would like to be able to retrieve all content (including user-done page breaks) as one long HTML string. I was considering to split pages in the state, but maybe it is better to somehow render automatically.

So, in short: I need my text to automatically split into pages, but be editable as one long string.

What would be the best approach to doing this?

For an example, look at https://youmescript.com/.

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