You can delete items copied to the clipboard or states in the Undo History palette to free up memory.
To clear memory used by the clipboard, choose Edit > Clear > Clipboard Contents.
To clear memory used by the Undo History palette, choose Edit > Clear > Undo History or choose Clear Undo History from the Undo History palette menu.
To clear the memory used in both the clipboard and the Undo History palette simultaneously, choose Edit > Clear > All.