I would recommend always keeping it in raw format until you want to print or publish online. At that time convert to JPG and save a copy, keeping the original RAW. For adding watermark there are extensions (plugins) available in Photoshop. There probably are stand alone programs- just do a search online.Actually managed some good photos this week while diving .
I was shooting in RAW format.
So once I go through crop etc , what format should I save in and how do you add copyright / signature to photo?