This WordPress plugin will automatically add a watermark to photos uploaded to media library.
Watermark can be text, image (png or gif) or both. Plenty of options can be set – from position, and size of watermark – separately for different types, text color, transparency and font, size of target images. It is able also to rotate uploaded images by exif data. Plugin also allows manual watermarking from WordPress media library or direct of files from upload plugins directory.