1 Okular
Okular is a universal document viewer developed by KDE. It works on multiple platforms like Windows, Mac OS X, Linux, and mobile.
2 Sumatra PDF
Sumatra PDF is a versatile free software that can quickly open many different file formats. It’s a stripped-down version of a reader, but it pays off because the software is sleek, quick and almost crash-proof.
3 Skim
Skim for Mac OS is akin to Sumatra PDF for Windows, a stripped-down PDF reader which works quickly and soundly, for every one of us that doesn’t need a bloated version of Acrobat Reader.
4 PDFChef
If you’re looking for ways to merge, split, rotate, and organize PDFs, and convert files to and from PDF – try PDFChef. This solution is an online editor for PDF files. With this fast and easy software, you can edit, merge, split, and rotate PDFs, delete pages, and convert files for free. Use this simple tool to organize your PDFs and rearrange pages in no time.