If you're going to make a book for electronic reading, PDF is a bad choice. A webpage/website is much better. A well-made website adapts to the equipment used to read it, and ideally it can offer the reader options regarding font size, light/dark mode, and so on. It also lets you have multiple instances of the same document open to different places – e.g. one tab for the map, one tab for room descriptions, one tab for each monster, one tab for each spell or special ability used by those monsters, and so on.Wrong about that. Many are using tablets or eReaders for content consumption, and those have limited storage and limited RAM.
My 10.5" likebook's page turn rate is severely limited by document size and complexity. Sentinel Comics was pretty much unusable. Alien PF was pretty quick, Similar sizes, but very different complexities, and very different UX. Both are much slower than the SC preview printer friendly, which is 22 pp... it can move the majority into RAM and then generate faster page turns.
Which reminds me: the Sentinel Comics adventures are pretty well tuned to be ready to run with a read through or two.
I have run adventures both from PDFs (e.g. PF2's The Show Must Go On and whatever part 2 was called, as well as various ETU adventures) and from D&D Beyond (Princes of the Apocalypse), and from a technical POV D&D Beyond blew PDFs out of the water. The adventure itself wasn't as good, but the technical side of things worked much better.
I get that if you primarily publish hardcopy you design for that, and then you essentially get a PDF "for free" as part of that process (though ideally, you'd massage the PDF some to put in bookmarks and hyperlinks and stuff). But if your primary channel is digital, PDF is a bad option.