If you have a legitimate license but lost your 18-digit key, you can find it through these official and technical methods: Search Email Invoices:
Finding the serial number from Installation ID Nitro Pro 10 Serial Number Key Finder
Nitro Pro 10 was released by Nitro Software, Inc. around 2014. It was a direct competitor to Adobe Acrobat, offering features such as: If you have a legitimate license but lost
Nitro Pro serial numbers are usually sent via email at the time of purchase. Nitro Pro 10 Serial Number Key Finder