Sumatra PDF Portable

y able to read PDF files, but it can also open ePub, MOBI, XPs, DjVu, CHM, and CBZ files, so you can always rely on this program when you need to carry files on a USB to open them on another computer. As it's a portable app, it's very light and fast, so you'll have no problems uploading the files, and you can use the app with any USB flash drive, even if you don't have much space.