SumatraPDF is described as 'A free, open-source viewer for Windows, supports PDFs, eBooks, Comics, with a simple, fast, and portable design prioritized for ease of use' and is a leading PDF Reader in the news & books category. There are more than 100 alternatives to SumatraPDF for a variety of platforms, including Windows, Linux, Android, Mac and iPhone apps. The best SumatraPDF alternative is Foxit PDF Reader. It's not free, so if you're looking for a free alternative, you could try Foxit PDF Reader or Okular. Other great apps like SumatraPDF are KDAN PDF, MuPDF, KOReader and Adobe Acrobat Reader.
Extremely barebones, missing and incomplete features like page-at-a-time scrolling, bookmarks and context menus. It's like a beta version. It functions... but unless you're on a raspberry pi or something and need the light weight, just opening files in your browser is more functional.