Copy link to clipboard
Welcome to the Lightroom Community. I'll help you figure this out.
Images that have already been exported with a watermark will not be customized again in this process. You can change the watermark in Export As > Enable 'Include Watermark' switch > Customize page.
Check this to learn more: https://helpx.adobe.com/lightroom-cc/using/save-share-export-mobile-android.html