Aperture plug-in developer Reinhard Uebel has updated his BorderFX plug-in. BorderFX allows the user to add borders to images as you export them.
New in BorderFx 1.0.4 is support for titles and copyright text; fixed a bug in the image scaling and border alignment; and Leopard support has been improved.
Using the plug-in you can fit an image within defined dimensions, adding borders to pad the image. Commonly used output options can be saved as a preset for quick access and you can add a watermark to the exported image.
The plug-in is free to download and use.