Here's a piece of freeware I'd forgotten about, I used it a few years ago.
http://www.snapfiles.com/get/tsrwatermarkimage.html "TSR Watermark Image enables you to add custom text or image watermarks to your photos. The program can optionally resize your images in the process and also convert them to JPG, PNG, TIFF or GIF format. You have complete control over the watermark location, size and transparency settings and can preview the results on a sample image you choose. Other features include batch processing, support for automatic EXIF rotation, angled text and text effects. TSR Watermark Image can preserve existing EXIF date and also add your watermark text to the EXIF copyright information for each image."