What are PDF downloads?
Google Books has always helped users discover and read out-of-copyright books online. With the addition of PDF downloads, Google now allows Internet users all over the world to download (and therefore print and read offline) these same out-of-copyright books. To find books that you can download free of charge, use Advanced Search and narrow your results by online availability. Click the Download or eBook - Free button on public-domain books to download a PDF of the book to your computer.
Some Google eBooks are also available as PDF downloads once they've been purchased. These downloads may be secured with DRM (Digital Rights Management), which may restrict the ability to print them.