Can he figure out how to build a charger for that e-reader from scratch? Wall sockets are going to be different in a millenium, if they even exist at all. With no manual, they could easily fry it with too much voltage before they actually get it working.
Same way they know now. Humans will still be humans. If my 3 year old son can figure out how my e-reader works from nothing, so can future humans.