You usually assign a default lifecycle policy to the document class. This helps users consistently apply the same lifecycle policy when adding new documents to the Content Engine.
However, the Create a New Document wizard provides the flexibility of selecting any lifecycle policy, even if it isn't the default policy for the selected document class. You can also remove the default lifecycle policy from a new document by selecting <none> as the lifecycle policy (instead of using the default policy assigned to the document class.)
Once you have assigned a lifecycle policy to a document, you cannot remove it from the document. In addition, you cannot assign a lifecycle policy to an already existing document.
To assign a document lifecycle policy to a new document