Sure, you can establish a stronger tie between the token and the file by embedding the chain ID, contract address, and token number in the content or metadata, but there’s no way to enforce that tie at the blockchain level. Anyone can still mint a copy with different metadata on a different contract.
As for legal documents, while storing them on-chain might help with transparency or timestamping, the blockchain itself has no legal jurisdiction. It doesn’t have legal authority, and documents stored this way are not inherently compliant with local laws, so they’re unenforceable unless recognized by a traditional legal system.