Thanks for your query.
Well, yes you may determine if a license is set of not by using Workbook.IsLicensed Boolean attribute, see the document for your reference:
Determining if the License is loaded successfully
Hope, this helps a bit.
MyUserName:For the latest Aspose.Pdf what is the way?I’m unable to find IsLicensed on Aspose.Pdf.DocumentHere is the documentation
Determine if license is applied
If a license is not applied, an evaluation watermark appears in resultant file. However before the resultant file is saved, you may have a requirement to determine if a license is properly instantiated. In order to accomplish this requirement, a static read-only property named IsLicensed is added in Document class.// determine if the API is licensed
// print message that license is applied