We’re looking into your requirement at our end and you’ll be updated with the results shortly.
I’m sorry to inform you that Aspose.Pdf for .NET only allows you to sign the PDF using the signature from the PFX file. It doesn’t allow you to sign the PDF from the KeyStore at the moment. However, I have logged a new feature request as PDFNEWNET-29354 in our issue tracking system. You’ll be updated via this forum thread once it is supported in future.
We’re sorry for the inconvenience.
The issues you have found earlier (filed as PDFNET-29354) have been fixed in Aspose.PDF for .NET 19.3.