Sumatra PDF
PDF, eBook (epub, mobi), comic book (cbz/cbr), DjVu, XPS, CHM, image viewer for Windows.
Small, fast, customizable, free.
Latest release: 3.4.6
Everyone loves SumatraPDF

SumatraPDF is one of those amazing open source programs that does everything a closed-source and/or commercial product does, but better in every way.

"PDF readers have, over the years, managed to earn themselves something of a reputation for being slow, lumbering beasts – thanks largely to Adobe Reader. Sumatra PDF bucks the trend. It is small, svelte, lightweight and lightning fast."

I was tired of using slow loading & bloated Adobe pdf-reader.
I found SumatraPDF. I'm happily using the portable application.
Thanks to its simple user interface, small memory footprint & fast startup.

The best PDF reader I have used since I started reading PDFs in 1998 is SumatraPDF.

Lightweight, fast loading, minimal resource hogging.

SumatraPDF v3.4 is the bomb! What a great piece of software by @kjk . The custom-keybindings work like a charm!
Made by Krzysztof Kowalczyk