Hi,
Thanks for your message.
This warning is due to that you were using our Spire.PDF commercial version without applying a valid license. We have sent a temporary license(one month free) via email to help you remove the warning message and evaluate our commercial version better. You can refer to this tutorial (Licensing) to use the temporary license.If there is any other issues, just feel free to contact.
Best Regards,
Herman
E-iceblue support team