Culling a document will hide it from view and prevent it from being returned in searches. For example, if you identify a set a documents as spam you can cull those documents so that they're not returned in your search results. Culling a document doesn't delete it, your document is simply sequestered in a "culled" collection that you can access again if you need to.
You can cull individual documents from your document list by clicking on the "Cull" button on the right-hand side of your document.
You can also cull individual documents from the document viewer by clicking on "Cull this document."
Click the "Culled" view button at any time to search, tag, and view your culled documents. You can also uncull them from the culled set at anytime (culling is not permanent).