https://www.zotero.org/groups/
With groups, you can collaborate remotely with project members, set up web-based bibliographies for classes you teach, and so much more.
YOU HAVE TO CREATE A ZOTERO ACCOUNT TO USE GROUPS!
It is possible to work collaboratively with Zotero by sharing references and PDF files. To do so, a Zotero account is required.
From Zotero, click the New Library dropdown menu ( New Library dropdown ) and select “New Group…”
Choose a group type
Click “Create Group”
After creating a group, it is possible to modify a few settings.
Types of members
If synchronization is activated in Zotero, groups will appear in the left column under your library and collections.
However, you can access groups without using Zotero by accessing them directly through the Zotero Web site. It is possible to copy references from your library to a group.
You can also work from a group collection without the references appearing in your personal Zotero library.
It is possible to share PDF files in a private group or a public, closed membership group. Modifications made to PDF files by a group member are visible by other members.
Of note, the size of files shared in a group counts towards the online storage space of the group owner (for Zotero, each user has 300MB of free online storage space; group files are counted as part of the space allocated to the group owner; additional storage space may be purchased).