Signing with smartcards might be challenging as they usually restrict private key export and only allow signing via own custom api, integrate with existing cryptoserviceproviders (windows cryptoapi) or provide an implementation of PKCS#11 cryptographic token interface.
If you need to implement an advanced signing workflow using smart cards, we can help you on the way as our products are fully compatible and provide extensible interfaces for these purposes. Should you have any questions, just let us know and we'll be happy to help you.