If you have lost your Nitro Pro 9 serial number, you can try the following:
Enter your Serial Number and the Installation ID into the web form. The website will provide an "Activation Code." Nitro Pro 9 Activation
Nitro Pro 9 is a legacy version of the popular PDF productivity suite, known for its balance of speed and professional features. While the software has been succeeded by newer versions, many users still rely on Nitro Pro 9 for its familiar interface and permanent license model. However, activating or reinstalling this version today can be tricky due to changes in Nitro's support systems. If you have lost your Nitro Pro 9
The software will generate an "Installation ID." Copy this ID. Nitro Pro 9 Activation
Visit the Nitro Activation webpage on a device with internet access.