For attachment files (PDFs etc), you can use linked files in such a location, if you can live with the limitations (they don't work with Groups or the mobile apps or the web library). You are responsible for syncing those files across computers (ie via the cloud service), instead of Zotero's file sync. You can use the delitem plugin for deleting linked files (Zotero does not delete linked files when deleting items).
https://www.zotero.org/support/attaching_files#linked_files
https://github.com/redleafnew/delitemwithatt

The Zotero database folder on the other hand should not be stored in such locations. Zotero's online data syncing is free/unlimited.
https://www.zotero.org/support/preferences/advanced (see Unsafe Data Directory Locations)