Synced files can be shared on the Web and in Salesforce1 by using the Synced filter. Share a file from the Salesforce Files folder by right-clicking the file and choosing a menu option under Salesforce Files. From the right-click menu, you can share with people in your organization, Chatter groups, or with people outside your organization via link. You’ll then be directed to Chatter to finish sharing the file.
If you share a file with a person or group with Collaborator rights, then when collaborators download, edit, and upload a new version of the file, you’ll get the latest version automatically synced. When you edit and sync a new version of the file, the people and groups you’ve shared with will automatically get the latest version on Chatter.