It is free, but you will have to register: Books and Resources | Hesperian Health Guides You can also find it on Amazon: Amazon.com: Where There Is No Doctor (9780942364156): David Werner, Jane Maxwell, Carol Thuman, Carol Thuman, Jane Maxwell: Books Peter
This is a good book to have on your shelf. But, if you're going to download it, you should also print it out. Nothing beats a paper copy when power runs out.
I like supporting Hesperian, so I bought bound copies of all their books, (Where there is no doctor/dentist/midwife/rocket surgeon).