Hi Elie,

First, sorry that you have problems using our plugin – it’s intended to help people, not to mess up their work. But I think you have misunderstood the idea of watermarking. Watermark, to be effective, must be merged into a digital file (an image or sound). Otherwise it would not serve it’s purpose – to protect from usage in original form.

What you did can be reverted tough. If you followed the instructions, you have watermarked only image sizes other than the full size image, which is the original file as it was uploaded to the site. Other image sizes are generated from it. So if you applied watermark to those generated images, you can regenerate them from the original file using plugins like Ajax Thumbnail Rebuild or Regenerate Thumbnails.

The procedure is described in the reply above.