One of the great features of AdWords is that you can change your ad copy at any time to match the latest promotions. Unlike with traditional print advertising, changes you make can go into effect within minutes.
If you have a high performing ad, do not edit it; pause it instead, creating new ads when you want to run special promotions. If you edit a high-performing ad, that resets its history back to zero.
To edit a single ad, perform the following steps: