This trips people up a lot once they do anything involving cross-referencing or bibliographies. But for some reason some people use latex for a long time and never hear about latexmk, which automates all that, and can even "watch" your files so you can edit and save and see your PDF refresh all in real time. (I've only used latex for papers or blog math, not big books; I can't imagine waiting a minute per change back in college, let alone on modern hardware...)