Is there a way to upgrade package contents after booking?

I have a client that booked at a lower package but wanted to upgrade. What do you recommend for doing that? I've changed their package contents but it didn't show up on the contract. I wanted to have the contract read the same contents so I just rebuilt it. I guess you can add them in on the addendum, but I figured it wouldn't make a lot of difference if I just started a new contract.