Thank you for contacting support. Each Aspose license has an expiry date and remains valid for the versions, released under the specific time period. You can open license file using an editing tool like notepad and check the value of ‘‘subscriptionexpiry’’ tag. Your license will never be expired if you use the Aspose binary version whose release date comes under the validity period of your license, it will work forever. Once you know the expiry date of your license, then you can download an appropriate Aspose.Pdf version from the download section: Download Aspose.Pdf for .NET APIs