To remove advertisements on your Invitations, Save the Dates, and Digital Cards, you would need to upgrade to a Punchbowl Platinum or Business membership.
You can review the membership features and cost here
Once you purchase a Platinum or Business membership, the option to remove ads will immediately be turned ON for all of your invites. You can adjust this setting from the Invitation Options
menu under the Member Features
: Ads can only be removed from accounts with an active membership. If you were to cancel your Platinum membership, your invitations would no longer be ad-free.