Mendeley is a free software that will help you manage your research, annotate PDFs, and format citations.
Mendeley has both a cloud-based and desktop component. First, you will create an account with Mendeley, and then once you've downloaded the Mendeley Desktop software, it will prompt you to log in with your account. There are also free mobile apps available for both iOS and Android.
Note: Mendeley has recently released a new version of its product called Mendeley Reference Manager. This is a different product than the Mendeley Desktop, although they offer very similar services. For more information about the differences between these two guides, please see the box below.