To create a new document in the Separation Workspace by using the Split option:
In addition to using the Split button in the ribbon, you can also use the scissors icon to separate documents. To use the scissors icon, place your mouse pointer between pages in a document so that a dotted-line and scissors icon appears between the pages:
Click this dotted-line to split the document. Pages after the dotted-line will become a new document. This new document will appear below the document from which it was split in the Separation Workspace.