A search is absolutely necessary for me. With a little development experience, a static search can be implemented quite well with the Stork Search project ("https://github.com/jameslittle230/stork").The video "Creating a Custom Menu with in5" ("https://www.youtube.com/watch?v=VPQBgn7BLZ0") shows how to integrate a "Top Menu". Instead of a navigation, a search field can be integrated which then works together with the self-generated full text index of Stork.
Here the result of a little test:
The static index can be created e.g. from a list of self-defined keywords, or e.g. from the texts of the respective pages of the PDF. Instructions for creating an index and the general integration of "stork search" can be found here: https://stork-search.net/docs
Are there any other suggested solutions?