Getting Evaluation Copy message

We keep getting error message -“Evaluation Only. Created with Aspose.Words. Copyright 2003-2007 Aspose Pty Ltd.” sporadically.
We can not reproduce the error, the error occurs like once in 500 letters that get printed, on the top of the printed letter the error is printed in red color. We are using licensed version of the software. I had a chat with online representative, He asked me to post the question on the forums as he could not resolve the issue. I am using the conventional method (using Aspose.Words and Aspose.Pdf) to create the documents.
Please help

Hi

Thanks for your inquiry.
Please check the points described in “Licensing” section in FAQ:
https://forum.aspose.com/t/aspose-words-faq/2711
Also, please follow the link to learn when and how you should apply the license:
https://docs.aspose.com/words/net/licensing/
Best regards,