How to make a stylish guidebook for iOs

iOS and iPadOS

Hi all.
I need to do a guide book for something and want it to be stylish.
Is there an app that will let me make a stylish index and chapters and stuff? I doubt it will be printed but I want it to look cool and profesional.
Maybe pdf? Or maybe html?
I only have my iPad but am using a keyboard to it so writing is okay but I need a stylish format with clickable index and stuff.
If the solution is HTML I need a html viewing app that is accessible.
PDF I am not sure if that is doable.