Sumatra PDF is a free pdf reader which is very light and fast. I recommend Sumatra PDF for these two reasons:
Sumatra PDF website
- Sumatra PDF updates the file when you change it. So you don't need to close the pdf file everytime before editing your LaTeX file and compiling it again.
- Sumatra PDF works very well with the backwards search option of LaTeX. If it is installed properly, when you double click on anything in your pdf file, backwards search highlights the corresponding area in your LaTeX file.
Sumatra PDF website