The split screen (Window>Split/Spreadsheet split) is useful for some workflows (especially the spreadsheet split where you can see your column headers and your data at all times), but to truly work in two instances of your document, I would recommend to select Window>New Window. This will create a new window that also displays your PDF file. Now you have two application windows that both display the same document. Both windows can be configured to look exactly the way you need them (e.g. page thumbnails in one window, and bookmarks in the other).
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
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