You would need to reupload the original image itself again.
Permanent Watermarking is just that permanent. It is embedded into the image which means the file is changed. As Conqsoft suggests you need to restore original images. This is why ON THE FLY watermarks are so popular since in essense they do not destroy the original.
well if you do not want to permanently watermark images then you turn watermarks to off. If your running gd on your server here are the three options you want checked to do OTF watermarks
In Admin =>Image Protection => Options
Enable on-the-fly image protection
This option uses the watermark.php script to serve images
When using on-the-fly image generation, do you want to overlay the watermark image?