The exception is "Specified argument was out of the range of valid values".
Using Aspose.Words 14.3
var options = new Aspose.Words.Saving.PdfSaveOptions();
var doc = new Aspose.Words.Document();
options.ExportDocumentStructure = true;
doc.Save(@"c:\temp\test.pdf", options);
Thanks for your inquiry. While using the latest version of Aspose.Words i.e. 14.3.0, I managed to reproduce this exception on my side. I have logged this issue in our bug tracking system. The ID of this issue is WORDSNET-10077. Your thread has also been linked to this issue and you will be notified as soon as it is resolved. Sorry for the inconvenience.