Zotero
Similar to other tools Zotero is a tool for collecting, sharing and citing scientific articles. It has well made extensions and offers a browser plugin to instantly download and add the citation to your library.
Base Application: https://www.zotero.org
Connector: https://www.zotero.org/download/connectors
Plugin: ZotFile
Manages your referenced pdfs locally and performs actions like renaming and moving them.
More: http://zotfile.com/
Plugin: Better BibTeX for Zotero
In a nutshell: This plugin offers improved export functionality for Zotero. When exporting your collection into a bib(la)tex file simply choose Better Bib(la)tex and your good to go!