Before starting configuring your watermarks, take a look at the General settings tab in YITH > Watermark.
From this page, you can make a backup copy of all the images of your store, so that you’ll be able to restore them at any time without the watermark.
As soon as you install the plugin, it will back up all the images, but if you add more images, it’s up to you to use this backup feature to keep your backup always up to date.
Click on Backup to make a copy of all your images.
Also, you can apply all watermarks that you’ve created at once by simply clicking on Apply all watermarks.
And finally, if you click on Reset button, you’ll be able to delete all product images with a watermark and restore your older images. Please, note that once completed, you have to deactivate the plugin and regenerate image thumbnails.