What you need is to record a script then run it in batch mode on the range of images.
Joe Frome then head programmer at Jasc added a Thumbnail 150 script to PSP8 that could be easily edited fro a largest side of 150,pixels to whatever you wanted like say 800 pixels. Then Gary Barton wrote resize to limit.
http://pixelnook.home.comcast.net/~p...izeToLimit.htm
He also has a watermark script on his site should you want it.

Its simply a case of opening an image and starting the script recorder run the resize script and then the watermark script or add a watermark in your own way. the save the script with a remember able name. now in batch process select your images and that script and a folder to save the results in rather then overwrite in case of errors