Google has been talking with book publishers about delivering digital downloads. Amazon already sells e-books while Apple's taken baby steps by supporting delivery of PDFs through its iTunes Store.
Make Magazine has published "The complete guide to PDF’s in iTunes," in which publishers who offer PDF's are profiled. They include, besides Make, Fader magazine, SkyMaul, some Rick Steves enhanced podcasts (photos and slides), and Slate.com for its tour maps of DC.
I'm not faulting Make. Its article is a good starting point to encourage more interest in the idea of using the Net for distribution of books and articles. Adobe (ADBE) is certainly supportive. It created the PDF format and its Acrobat Reader has become the standard tool for reading the files. The latest version of Adobe Acrobat 8.0, the PDF-creation software, generates what are being called PDFcasts which include bundles of documents. One use would be creating PDF’s about a company's customers. The files could be distributed to salespeople on the road so that everybody has the same information.
Publishers are described as wary in their talks with Google. Nobody expects PDF distribution of best sellers to become a big business soon. But niche publishers, like Make and DailyFrenchPod, are incorporating PDF files into their businesses now. It’s already happening.