This feature is only available in Commercial Versions. Please goto https://edu.ink to upgrade to a commercial version.
Once your payment has been made, your registration information will be sent to your email address in minutes. Then in the software, click menu Help -> Upgrade to Commercial Version, enter your email address and activation code.
After upgrading to Commercial Version, click the button Options in the main navigation bar, then in the Options dialog, you can uncheck the option Add Watermark to remove the watermark, or you can add your own text or image watermark.