How do I know it's real?

If you find a need to provide some sort of certification that your document has not been tampered with and is the rel thing, you might consider a digital signature.

This Microsoft Support article discusses the process.

What is a digital certificate?

What is a digital signature?

What occurs when I use a digital signature?

What Word files can I sign?

How can I obtain a digital signature?

• Method 1: Obtain a digital certificate from a certification authority
  
• Method 2: Create your own digital certificate