Changing the Document Permissions
By default, anyone can see and download a document. However, the person responsible for the document can choose to limit access to the document to some contributors and/or groups.
Through the button shown in the picture below it is possible to manage the document permissions.
The Change Document Permissions button on the right side of the document page allows to set up who can:
View the document;
Edit the metadata;
Manage it (update, delete, change permissions, publish/unpublish).
See an example in the picture below.
Usually editing of metadata and the management of a document is made by the person responsible for the document, i.e. the contributor who uploaded it and who has those permissions by default.
Once the permissions are set, click Apply changes to save them.