Notes:
All credits belong to Affinity team :) It is not 100% copy of original Help in AD. The formatting is slightly different (page layout, bullets, colours, etc.) so don't be confused. The file format is .ibooks. Sorry, I didn't use EPUB or other but I guess every user has iBooks installed :) Sorry if some references / hyperlinks are missing. I use old-fashioned "copy&paste" method to create this file. I've exported this file from iBooks Author to PDF too, but for some reason the hyperlinks don't work. Anyway if you prefer PDF here is the download link.