An ebook (eBook, digital book) is the digital equivalent of the traditional printed book. For Ellibs Ltd, a digital book refers to an ebook in Adobe PDF format, which can be read using the Adobe Digital Editions software.

The PDF format developed by Adobe represents a standardized means of storing, editing and printing ebooks. Since the reading/printing of books in the PDF format is easy - and the program is available to most computers and operating systems - it is commonly used on the Internet.