Zotero is a reference management software that helps you collect references, track associated PDFs, and generate bibliographies. (Link)
Pricing
Zotero is free and open source, with a small amount of free cloud storage. More storage is available for purchase.

Although Zotero works well out of the box, I use the following plugins and configurations to improve my experience:

  • Install the Zotero Connector for your web browser (available on the Zotero download page).
  • Change Zotero settings to store PDFs in Google Drive (or your own choice of cloud storage).
  • Install the Better BibTeX for Zotero extension to improve the process of exporting to LaTeX bibliography files. In particular, Better BibTex offers automatic exports, stable citation keys with a customizable format (these keys are what you reference in LaTeX with \cite{key}, so sensible values can greatly improve the readability of your code).