A company has limited liability. That means if it goes bust, the liability of the shareholders is limited to the share capital of the company.
So it's very important that anyone with whom the company is dealing, knows that they are dealing with a limited company.
So the full name of the company , including the fact that it is limited, must be on all documents.
If you print headed paper in the name Renocco rather than Renocco Limited, not only would it be an offence under the Companies Acts, you would probably lose the protection of limited liability if anything went wrong.