I make a Photoshop brush out of mine, and of my copyright notice. Do this:
-Open your logo in Photoshop
-Edit>Define Brush Preset
Now your logo will be a brush in your brush presets, and you can adjust the size and transparency each time you use it. Always go Layer>New Layer to apply it. That way you can move it around as needed. (Pro Tip: Save your brushes to your computer somewhere) Now this method requires you to add it manually to each individual image. Someone out there might have a techie way of doing it in batches somehow, but this is how I, the opposite of a techie, do it.