To add to the other comment, Zotero can also download the PDF for you if you just have a citation (if it can find it) and it also integrates into Word, Google D

To add to the other comment, Zotero can also download the PDF for you if you just have a citation (if it can find it) and it also integrates into Word, Google Docs, etc. for citations when writing research papers. It's especially useful for multiple people writing the same research paper as the library can be shared.