There are two ways to set a document in edit mode:
Clicking on the 'edit' button in review mode. If
you do not see an edit button on an existing document, you probably have no
permission to edit the document. In the standard configuration, only the one who
created the document may edit it later. Even the CMS
administrator may not edit a document in the CMS that was created by someone
else. However, he always can via the web
console. Permissions can be configured
by the CMS administrator.