If you need a lightweight PDF Reader, you may want to try Foxit Reader. Faster than many big competitors like Adobe Reader, it consumes little RAM and hard drive space.
We often talk about software to create, merge or edit PDFs. What can you do when it comes to protecting PDFs from text edits and copies? There is specific software for that. PDF Anti-Copy is an interesting one: it's an incredibly simple solution, but one that does what it promises.
Adobe Acrobat Reader DC is one of the most powerful PDF software in the world, and although a lot has changed in the last few years, Acrobat still is the software of choice for your pdf reading needs. It’s a free download from Adobe’ site.
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.