PDF or Portable Document Format file is popular eBook format which is created by Adobe system. An electronic book or eBook is a book length publication in digital form that consists images, text, etc which readable on computers as well as other electronic devices. Sometimes, it is defined as ‘an electronic version of a printed book’. Many ebook readers support pdf documents but unfortunately all the pdf documents does not provide ease while reading on small ebook reader screen. Thus, EPub or Electronic Publication is free and known to be the open source standard for eBooks by IDPF. It is the most popular eBook format supporting all the readers such as iPhone, iPod, iPad etc. It is same as html stream.