It is also possible to use your existing cloud storage (Google Drive, Dropbox, etc.) to store these attachments. See our Advanced Zotero page for instructions.
Backing up your library
Syncing your library is not the same as saving a backup.
Your Zotero information is stored on your computer, so if you perform regular backups you should be able to access a version of your library if necessary. It is also possible to locate your Zotero information and save it to an external device. Instructions are available on the Zotero support page.