If you have purchased PhotoZoom Pro 4, you can unlock it by entering the unlock code that was delivered with the software.
In case you have not unlocked the software yet, the unlock window will appear automatically when you start the program (either the stand-alone version or one of the plug-ins):

Some unlock codes only work in combination with a specific name and email address. In such cases, the required name and email address will be clearly specified with the unlock code. Please make sure to fill in all info exactly as specified.
If you have purchased this software as an upgrade, make sure to select the upgrade option first and then enter all unlock info as indicated by the software.
You only need to enter your unlock code once in order to unlock the software permanently. Also after installing free updates, you won't have to enter the unlock code again.
Note that as long as you have not unlocked the software it will be running in trial mode, which involves one restriction: the images you save will contain a watermark. While the software is running in trial mode, you can open the unlock window any time by selecting "Unlock..." from the Help menu.
If you purchased the software online and received your unlock code through email, we highly recommend to fill in your unlock info using copy/paste. This may avoid typing errors.