While in Quick Info Edit mode, and if the DOI/ISBN Sniffer quick edit assistant is activated (on by default), it will search for valid DOI and ISBN numbers on the document first page text content, and in any of the metadata fields shown in the InfoEdit tool, and present the manual DOI/ISBN resolver tool, if any found.
But I have now found out that this assistant is only firing (and I must fix this) when the open PDF file changes, after being already in Quick Info Edit Mode, so, to see it in action, you will have to enter the Quick Info Edit mode, and then change to a document with a valid ISBN (including the dashes, e.g. 0-123456-47-9) in any of the visible metadata fields, using the bottom left toolbar navigation buttons, numbers 5 and 6 in my previous reply linked manual page, or its respective CTRL+Up and CTRL+Down, keyboard shortcuts.