If your Confluence is linked to you JIRA Service Desk, you can define one space to be your Knowledge base : https://confluence.atlassian.com/conf53/developing-a-knowledge-base-on-confluence-wiki-411108858.html, and open it publicly, while the other Confluence spaces remain private.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.