I love my kindle for this reason! I put almost all of my knitting patterns (that I'm currently using) onto it, and that way I always have them with me. I can carry several patterns with me without worrying about pages getting lost or crumpled .... I know that everything's always in one place.
Kindle's come with a USB power cable, so you can just connect it to your computer that way to transfer files or you can do it wirelessly as one of the pre-posters mentioned. Either way, it's very simple!