You need to upgrade to Aperture 3.4.3.
And the upgrade is free. Did you buy Aperture from the AppStore? Then you can upgrade it from the AppStore by signing into the AppStore with the AppleID you used to buy it originally. To be able to see the update, your Aperture application must be named Aperture, not Aperture 3.3.2 or similar, and it must be located in the Applications folder, ot a subfolder. You should be able to download the update from the "Update" tab in the AppStore, not from the "featured" tab.
If you bought Aperture from the Apple store and have a serial number, use Software Update to update, not the AppStore.