When trying to activate FineReader with a serial number, the error message appears:
Invalid serial number.
Misprint in the serial number which you are trying to use for the program activation.
Or the license you are trying to use corresponds to a different version of FineReader: "This serial number cannot be used for ABBYY FineReader PDF" error during activation.
To resolve the issue, please check the correctness of the serial number you enter.