Website: http://www.pcwinsoft.com/batch-photo-watermark-software.asp
Download: Pcwinsoft_Photo_watermark_studio-2.5.5.50-gotd.zip
Photo Watermark Studio is designed with the best practices on watermark photos in mind.
Photo Watermark Studio allows you to overlay your photos with transparent text stamps and transparent image stamps. The program supports a great deal of fonts and several effects can be applied to text including colors, rotation, shadow, underline, and more.
On my system it has a horrendous memory leak and with just a 5 megapixel photo it repeatedly increases memory allocation up to 1533MBytes then throws an out of memory exception that can be Continued from by pressing the Continue button and it starts again… if one times the watermarking at the low end of memory (ab)use it does watermark ok but does not support .webp file opening or saving that is claimed in the original giveaway description.