We recommend Watermark Plugin by dFactory to add watermark to the photos.
1. Install "Image Watermark" Plugin
2. Activate the plugin
3. Go to plugin settings
4. Set all checkbox (Square is used for user photos so you can leave it unchecked, myhome-estate-min is used for single property gallery thumbnails so you can leave it also uncheck)
5. Check post type: "estate" and "Enable frontend image uploading"
6. Choose your watermark and its position e.g.
7. Save Changes