Here's how you might see it used:
* "Join us as [Name] receives their Doctoral Degree in [Field]."
* "[Name] is proud to announce the completion of their Doctoral Degree."
However, there are a couple of exceptions:
* If you're using the abbreviation "Ph.D." or "Ed.D.", you don't capitalize it.
* If you're using "doctoral" as an adjective, you don't capitalize it. For example: "We are excited to celebrate [Name]'s doctoral studies."
Ultimately, the best way to ensure consistency is to check the specific style guide of your institution or the graduation invitation template you are using.