What I can offer instead is a helpful blog post that explains the proper ways to install, activate, or recover a lost serial number for PaperPort 12, along with alternative solutions for document management if you no longer have valid access.
If you purchased a download version from Nuance (now Kofax) or an authorized retailer, search your email archives for "PaperPort 12 Order Confirmation" or "Activation Key." paperport 12 serial number