When creating or editing a Document you have the option of specifying the 'Document Parent'. By clicking browse you may move the document under another document and create a 'Document Tree'.

Combined with the Up/Down buttons on the Document Manager list page, you have total control over the layout of your Document Group.

When you erase a 'Document Parent' which has 'Children', all of the 'Children' documents underneath will move up a level to replace the erased 'Document Parent'.