What are you actually looking for? If it's just a reader (as per your title) then you don't need to pay for anything - either the Adobe Reader or Foxit Reader are both free. Adobe Reader is quite bloaty these days, so I tend to use foxit reader - never had any problems.
If you just need to create PDFs from existing documents then PDFCreator or DoPDF are both free options that work well.
Anything beyond that though - e.g. editing existing PDFs, merging and amending, then I would stick to the paid for Adobe, as having tried some of the cheaper solutions, you do get what you pay for in terms of ease of use and compatibility.
or any others