- Save your watermark as a PSD (Photoshop) file with a transparent background.
- Create multiple sizes of your watermark so that you can select the one that is the best match for the output size of the exported image.
- After you create a watermark, save it as part of an export preset so you can reuse it as often as you need.
In Adobe Lightroom 3:
- From the Lightroom menu select “Edit Watermarks …”.
- Enter text. Hit Save.
So to use watermarks in Aperture 3, I need to use Photoshop — an expensive Adobe product?