If you are a legitimate owner of Acrobat X Pro and have lost your key, use these official methods to recover it:
Adobe has acknowledged the server shutdown. They offer a workaround for existing customers who need to reinstall CS6 or Acrobat X. You can often find a specific "Offline Activation" request code generator on Adobe’s official help pages, but this usually requires you to already own a valid serial number.
Offers a secure, modern alternative with an option to buy a license rather than subscribing. (Web & Desktop):