Install FlickrExport for Aperture

FlickrExport is a plugin for Aperture that provides advanced photo uploading to your account on Flickr.

The application can keep track of which photos you have already uploaded on Flickr. If you later edit a photo or its metadata in Aperture, FlickrExport can automatically replace the existing photo with the newly edited one, or just update the photo's metadata without uploading a new copy.