This problem likely occurs due to incorrect versions of files being installed. It happens when a user has both SignPro, and the Signature SDK installed simultaneously.
The key to correcting this issue is simply to install them in the correct order.
First of all, go to your Control Panel > Apps & Features (Features & Programs in earlier versions of Windows) > Uninstall SignPro PDF and Wacom Signature SDK.
Once the uninstalls are complete, restart your computer, then reinstall SignPro first, then the Signature SDK.
This should resolve your problem, but if not, please contact us for further assistance.