A PDF reader is any software that opens a PDF file, probably the most recognizable document format in the world. Your downloadable bank statements, your school newsletters, they're probably all in PDF format.

More and more operating systems, smartphones, and other devices have built-in capabilities to view PDF files; even your web browser can probably handle it. Still, a dedicated document reader often has a number of advantages over the built-in reader you may already have, such as viewing options, better searching, and annotations or other light editing.

I have been using SumatraPDF for years. It is an easy to use free PDF reader for Windows. While it is easy and simple to work with, it is also open to heavy customization if you want it to be.

There are different types of viewing modes available, such as Single Page, Facing, Book View and Presentation. The last option is great for distraction-free reading.