Latex is too hard for mortals, but I’d suggest Sphinx or one of the markdown alternatives. I think atlassian confluence is another even friendlier alternative, with a price tag.
Atlassian Confluence is a horrible recommendation; it has few tools for typesetting, PDF export is very mediocre and hard to control (there is a plugin that allows you to control pagination), and I once found something that was impossible to produce in its markup (my workaround was to insert a zero-width character and hope no one copied it into a terminal).
l o l
Replying separately because the other response is good and deserves upvotes, please vent your confluence antipathy on this comment’s karma instead.