Trapcode Particular is distributed as a fully functional unlockable demo. When running in demo mode the plug-in adds a watermark in the form of a red cross over the rendered frames. A License Key can be purchased at the Trapcode Website.
To unlock the demo into a full version apply Effect>Trapcode>Particular to any layer.
Then click at "Options":
In the Options Box, click "Enter Key...":
It is very important to enter both the name and the key exactly as received in the e-mail.