Yes, pin 7 of the DB-9 can be used to power the KPC-3+. Ground is pin 6. There are some jumpers that you'll have to set to accomplish this since that pin has multiple uses. From the manual:
"To power the KPC-3 Plus from Pin 7 of the DB-9 connector, you must connect J7 center pin and pin 2, [and] J6 center pin and pin 2."