well how things work depend on how you have it setup. Watermarking works in our application as well as other option all depending on your real issue your trying to contend with.
Permanent watermarking is not going to appear on photos just because you add a watermark path. You would actually need to watermark the images. After you enable watermarking and set category perrmissions for usergroups you can use the scan database option to watermarking non watermarked images in there.
On the fly watermarking would work on your gallery but the images are not really truly watermarked.
More information would definately be needed for me to truly ciomment on how to best handle your situation.