Hi VishalA,
Thanks for your inquiry.
The version you used is commercial version, so you will get the warning message without applying the license. At present, free Spire.PDF doesn't support .net core. But the feature will be added in the next version of free Spire.PDF. Note the update date is not fixed, we will only maintain free version when we have enough time. Anyway, once it is released, we will inform you.
Currently, to help you removing the message and better evaluate our product, our sales team has sent a one-mouth free license of Spire.PDF to you, please refer to
this guide to apply the license.
Sincerely,
Betsy
E-iceblue support team