MAKE has put together a guide to podcasts that pair audio with supplementary PDFs.
For example, the audio tours (pairing PDF maps with accompanying audio) by Rick Steves and the language lessons (pairing audio lessons with vocabulary PDF) by FrenchPodClass look like incredible podcasts; the supplementary PDFs bring an added level of usefulness to each one. The Makers have been taking advantage of iTunes' ability to manage and distribute PDFs along with podcasts for quite some time, and this list brings together several of the best PDF-audio pairings we've seen. If anyone already subscribes to an audio-PDF podcast, tell us about it in the comments.