Can this order be placed on a purchase card (as a method of procurement and a method of payment) because the price per page is a firm fixed price although the quantity of pages has increased?
The FAR provides general guidelines for use of the purchase card but the military departments and agencies establish their own procedures and limitations for use of the card. The new $120 total is still a "micro-purchase" so the FAR permits using the card to pay it. If there is something in Navy's purchase card program policy that gives you pause, then you should review the policy. Otherwise, I see no issue with using the card in your situation.