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.