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You do realize that under 'all' you are looking at every book you own, not what is downloaded to the device? So if you delete one of them, you are permanently removing it from your account and you will no longer have access to it?
Can find no way to delete items that show in the "All" section of my Paperwhite library. The documents are not actually on the Kindle but show. Is there anyway these can be deleted?
go to the Amazon website and like J.Penrose says, open the Your Content and Devices page (under the upper right menu), change Books to Docs and you can permanently delete them from your account. Be careful as there is no undo or undelete if you accidentally delete the wrong one