Showing thumbnails of another open document
To show thumbnails of an open document without switching to it
In the Thumbnails panel, on a document title bar, click the 
Show thumbnails button to the right of the document name. The document thumbnails of the clicked document will be displayed in the Thumbnails panel without switching to the document itself. The contents of the Page Image, Text Editor and Document Manager panels will not be changed, only the Thumbnails panel’s contents changes.
-
You can copy and paste pages between documents using the thumbnails, without having to switch between them.