Documents are created in the workbook by editors. They then go through an approval process that concludes with the document being published, after which it can be found under Published Documents. All document work, however, always takes place in the Workbook, and for this the user requires write access to the workbook.
To edit a document with the status Published, the user must open the document in the workbook, check it out, and change its status from Published to In Progress. The content can then be edited, and once the work is complete, the status can be changed back to Completed — at which point the approval process begins, concluding with a new publication of the document.
See the short video below for a walkthrough of these steps.