What is the difference between an eBook in EPUB format and an eBook in PDF file format?

The EPUB format is the standard format for e-books. E-books in EPUB format are optimized for use on mobile reading devices. They display dynamic content, meaning the flow of text automatically adapts to the screen size of the device.
EPUB (acronym for electronic publication) is an open standard for e-books and is supported by most readers (examples: Tolino Vision, Tolino Shine, Kobo Aura, Bookeen Muse or Pocketbook Touch). You can use EPUB files from Kosmos without additional DRM programs, just like PDFs.

PDF files are a platform-independent format for exchanging text and images. PDF formats are particularly common for specialist books.