Might be that I just can't find the obvious, but thanks anyway for your replies.
What I am looking for is an option to limit scrolling to the bookmark you're currently in.
For example, let's assume you want to assemble a book with different chapters organized by bookmarks. The first chapter is 5 pages long; is it possible to allow scrolling over those 5 pages, but when you come to the bottom of the 5th page, scrolling won't take you to chapter 2, so that if you want to get there, you have to use the bookmarks?
(Before you ask, the example is maybe not chosen well, but it's easier to explain it that way than with the actual project I'm planning to use this "feature" for.)
'Fraid not, scrolling is always over the entire document. Bookmarks are stuck lightly on the document, they aren't part of a high level structure that organises it, and bookmarks may not even link to pages.
It can't be done in a way that would work cross-platform or with non-Adobe software, plus it will make the application appear to be broken so it will annoy the living heck out of people.
The scripting solution would be to use bookmark actions to set a global variable marking the 'chapter', then to define Page Open events that forcibly change if you stray outside the allowed limit. The problem is that you cannot hide the page thumbnails, the scrollbar will act in a really strange way, and if someone manually advances with the page number field they can jump past the scripted event.
If you want a PDF to behave as if it were individual documents, make it that way then bolt the sections together as attachments to an index page, or in a PDF Portfolio.
I agree that doing it with a script is somewhat clumsy and far from ideal,
but what you said about navigating to a "forbidden" page with the page
number field is not correct. A script can be used to prevent that as well.
And thanks a lot for your quick and competent advise. As it is, it's more of a "nice to have" than a "must have" for the project, so I hoped for an easy built in-solution. I can see why this does not exist, though, so I'll do without it.
If you grab every page's event listener it will react to a selection from the page field, but to be at all sensible about the amount of scripting involved, I think you'd want to limit the page actions to those at the bookmark boundaries. There are also plenty of situations where page events aren't triggered (e.g. when scrolling a card in a Portfolio, or when someone's just disabled JS).