This is just so much easier to do when you have a schematic... I haven't tested this so it may not work but try: Select one then right-click and use Find Similar Objects... Set the criterion for the Footprint name to be Same then click Find. That will highlight all the footprints with the same name. Close the find dialogue box. The right hand panel will show the shared attributes of the instances of the selected footprint. Change the name to the new Footprint. If the Footprints are no longer highlighted, repeat Find Similar Objects ... but with the new Footprint name. In the canvas, do right-click Update.