Check your email: Search for keywords like "Nitro PDF," "Cleverbridge," or "Invoice."Nitro Portal: If you registered your product, you can log in to the Nitro Express or Support portal to view your order history.Registry Retrieval: If the software is still installed and activated on an old computer, specialized "product key finder" tools can sometimes extract the 18-digit key from the Windows Registry. A Note on Modern Compatibility
A dialog box will appear. Enter your 18-digit serial number exactly as it appeared in your purchase confirmation email. Click Activate. Nitro Pro 9 Activation
The software will generate an "Installation ID." Copy this ID. Check your email: Search for keywords like "Nitro