Citavi is a heavy weight tool which allows you to manage not only your publication data (you can link pdfs to the entries, etc.) but it is also a project management tool. You can organize all the literature you want to read, have read or you want to use in certain sections of your paper you are about to write. This might be very helpful for big projects as your PhD is!
There is also a plug-in for Word etc., so you have access to the database from your document and can select the proper citation style for the bibliography.
It is a great tool I recomment, especially if you can you the licence of the university. But is there anything not so good about it? Yes, unfortunately the development of Citiavi for macOS was abondend some years ago. If you have a Mac-computer you need to switch to another programm, such as Endnote or Zotero – which is explained below (or use a virtual Windows-environment…).
For some detailed information have a look at the Citavi-Info page of the RWTH library.
How to get a licence?
Browse to https://citaviweb.citavi.com/p/campus# and type ‘RWTH Aachen’, you will be redirected to the “Single-Sign-On-Site” of the university where you have to log in with your TIM-ID.
Then you can download the software for which you automatically get a licence for.