If you want to change the PID for the bootloader, it can be changed in the makefile. See 'arduino-1.0.5/hardware/arduino/bootloaders/caterina/Makefile'. Then recompile the bootloader and install.If you want to change the PID for your program, edit the leonardo entry in the boards.txt file. See 'arduino-1.0.5/hardware/arduino/boards.txt'. Then recompile your program and upload.