I do not think HTML tags will work in a PDF file it is not discussed within the documentation for the PDF standard.
Have you been able to get the documents to work on full computer and not a mobile device?
Do you want structures are available within the PDF?
I would look to see if there are articles or bookmarks you could reference.
If you cannot modify the referenced PDF do have any idea on how to return to your control app?
You say you are not allowed to change the PDFs. But do you mean you are not allowed to change the visible page, or that you must distribute unmodified files? If it is the second, I can't see how you could add a button (even if that would work) or any other kind of navigation or script - these go inside the file.
Unfortunately we are not allowed to modify the file in any way. The button should not be included in the PDF file. The sequence is the following:
1) There is a page with a button
2) The click on the button opens the PDF and navigates to a defined paragraph (e.g. to the headline "2. Example headline").
The PDFs we use do not have any bookmarks or references of some kind included.
So the solution has to be something that does not change the PDF but rather navigates to a certain page/paragraph of the PDF.
Has anyone an idea?
Ok, I imagine you will be writing an app and using the built-in APIs to display a PDF. These are part of Android/iOS and not any Adobe API, and will have quite different facilities and interfaces. They might display a live PDF with navigation or they might just display a static image of a page region, with you providing navigation/zooming etc. Or you might have a choice. Perhaps these platforms have APIs for text extraction by page, which can be used to search. Perhaps they even have a direct API to find text and display. Anyway, if you are writing an app, you need to now examine what the platform APIs offer.