Like everything else in Lr, the file itself is never changed. All edits are instructions implemented on the fly when the file is outputted to a device. You cannot duplicate output sharpening. You apply the strength of output sharpening that the application allows and you prefer each time you send the file to print. Though you didn't ask, in the same vein you will notice that once you implement one set of capture sharpen instructions in the Develop Module, those instructions cannot be duplicated. You will only see a new history step for capture sharpening if you change any of the parameters from their original settings.
