This structure implies a "live" manual. Unlike a PDF stuck in a game folder, a web-based manual accessed via PHP could be updated by the developers instantly. If they changed a stat for a Swadian Knight, they could update the manual on their server, and every player clicking that link would see the new data immediately.
To use the manual activation method, follow these steps as outlined on the TaleWorlds Forums : http wacttaleworldscom manualphp upd