Salesforce: How to make a Document public?
A public Document in Salesforce means that anyone can download the content even though they don’t have a Salesforce login to your instance.
To do this, you need to:
1) Make sure that this Document has “Externally Available Image” checked.
2) Get the URL of this document by using the following URL.
https://c.<server>.content.force.com/servlet/servlet.ImageServer?id=<Document ID>&oid=<Organization ID>
Since the server is located at eu1 and if the Org ID is 00D200000007C7C, the URL should be: