A certified copy of documentation provides you with a legally-viable duplicate of your Certificate of Documentation. To be in compliance, you must have a Certificate of Documentation on board your documented vessel while in operation.
A non-certified copy is invalid, as is a picture, a photocopy, something in “the cloud,” and so forth. If your Certificate of Documentation is lost or mutilated, you must have a Certificate of Documentation to maintain your documentation.
Vessel owners can obtain a Certified Copy of a Certificate of Documentation here.