By default, each chapter in your book and the book itself will build two different PDF files for download: mobile and printable. Mobile PDFs are optimized for tablet viewing, while printable PDFs are optimized for printing on U.S. letter-sized paper.
To make sure that PDFs are enabled on your chapter, while editing your chapter, click on Formatting and ensure that the PDF Rendering option is enabled. A similar option is available when editing the book's main page.
Once PDFs are enabled for your book or chapter, the download link will appear at the bottom of the page. However, PDFs must be built by the server in the background and may not be instantly available. Chapter PDFs generally take several minutes to build (depending on server load), and book PDFs may take a few days. This process can be expedited by the administrator upon request if needed.