Apple Books supports PDF and EPUB formats. As long as you open the e-book through the book app, users can read the book on iPhone, iPad and Mac at the same time after iCloud synchronization. In addition, users can also share the webpages they see in Safari into books, save the contents of webpages in PDF format, and consult and mark notes at any time. PDF stands for Portable Document Format, which means portable document format. It is a file format developed by Adobe Systems for file exchange, which has nothing to do with applications, operating systems and hardware.