iWorks trial, then bought KeyNote. Cant save.

Hi, i downloaded the iWorks trial, then bought KeyNote from mac app store. I have now created a slide show in KeyNote but it wont let me save it as my 30 day trial is over... Anybody know how to solve this? I dont want to redo my slide show, took me ages to do.

Very thankful for help!

Cheers.

Anders