Follow these simple steps to produce a nice watermark in Aperture:
- Create your watermark image. Popular software that can accomplish this include Photoshop or Pixelmator.
- Open one of your images in full resolution. This will give you a baseline for the size of your watermark.
- Create a new layer on top of your image. You can use either a text or image watermark. Using a background image for your watermark will make it readable no matter what the color makeup of your photograph is. The key to a good watermark is making it at least semi-transparent (so you do not take away from your photo).
- Be sure to export your watermark image from Photoshop or Pixelmator as a file format that supports transparency (.psd or .png are great formats).
- Creating different sizes of your watermark. Aperture will automatically do scaling on watermarks so that they fit exported images. However, to completely control the way your watermark looks on your photographs, you will want to export a version of your mark for each pixel ratio you have in Aperture.
- Add your watermark to an export preset in Aperture. Navigate to Aperture > Presets and choose Image Export. Add a new preset and rename it "Image with Watermark". In the Export Presets window, check the "Show Watermark" box. Choose the file you just created and where you would like to position it. If you included transparencies in your original watermark file, you can set the Opacity level to 1.0. Choose to scale your watermark if you want Aperture to decide how big your mark appears. If you have created a specific size, uncheck that box. Click OK and your preset is saved.
- Select the image you wish to export with a watermark. Navigate to File > Export > Versions (Command + SHIFT + E), choose your newly created preset and adjust the file naming settings to your liking.