Which service are you using? Is this a PDF form? Are you using Adobe Reader or Acrobat? If so which version (including minor)? Which platform/OS? Is "X" in your message a real character or a substitute for something else? I do not recall seeing this message.
Generally, the trust settings pertain to digital signatures but it does not seem that you have a digital signature problem. If you're using a server-based service it could be something that comes from this service and you need to ask them.