Do you use references in more than one location (work, school, home)? Do you want changes made in one Bookends library to be reflected in all? With library synchronization (sync) it's easy. Bookends uses iCloud to effortlessly keep your references and groups in sync across a local network or the Internet, so you no longer need to schlep your databases from one computer to another.
PDFs and custom folders can be maintained in and automatically accessed from a file-sync service folder of your choice (e.g Dropbox, Google Drive, Microsoft OneDrive, etc.), so they are always up-to-date as well.