Block Adobe Creative Cloud storage / saving

If you mean Adobe CC sync files, Adobe announced an EOL plan for that.

https://helpx.adobe.com/enterprise/kb/eol-cc-synced-files-for-business-plans.html

If you are referring to cloud documents like Document Cloud, Photoshop Cloud Docs, etc.

You can customize settings in the package and customize the preferences for the individual apps to disable cloud storage:
https://helpx.adobe.com/enterprise/using/package-apps-admin-console.html

Example with Acrobat:

https://community.adobe.com/t5/acrobat-discussions/how-to-disable-cloud-storage/td-p/12531312/page/2

Easiest road I've seen others post is to simply block the URL via Firewall.