We've been able to apply watermarks in Aperture since the beginning, but the problem is they usually don't look the way we want. Unless you create your watermark with a transparent background, you'll get what looks like a rectangular label instead of the more elegant type without a box.
The procedure for a better watermark is relatively simple. Start in Photoshop. Go to File > New, then choose "Transparent" for the Background Contents popup menu in the dialog box. Click OK. Once you've created the file with a transparent background, use the text tool to type and style your watermark. You may want to shade the text light gray instead of black (even though you do have an opacity slider later on in Aperture for fine tuning). If you want a diagonal watermark, go to Image > Image Rotation > Arbitrary and set the angle you want. Once everything looks good, then Save As Copy in the PNG format. You'll also want to save your master as a PSD file for easy editing at a later date.
Now go to Aperture. Pick the image you want to apply the watermark to, then choose File > Export > Version. In the Export dialog box, choose "Edit" at the bottom of the Export Preset popup menu. Click the "+" icon in the lower left to create a new preset. Set your basic parameters, then check the "Show Watermark" box. Click the "Choose Image" button and navigate to the graphic you created in Photoshop. If you go diagonal, you'll probably want to position it in the center.
Once everything is set up to your liking, click OK, then click Export Versions. You may have to run a few tests to get everything the way you want. Once you do, you can watermark many images at once by batch exporting from Aperture. You can also set up different export presets for watermarks placed in different positions, such as lower left and lower right.
I don't have to watermark often. But when I do, it's nice to have this set up ahead of time.
More Aperture Tips and Techniques
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