Sigil is a handy utility that was designed in order to help you easily create and edit your own personalized e-books in no time. It is a free and open source e-book editing application that's advanced, well-designed, comprehensive, user friendly and light on system resources.
Here are some screenshots to illustrate the features and user interface of this application:
Calibre
PDFCreator
Adobe Acrobat Reader DC
Doro PDF Writer
PDF Shaper