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You could already do that using OP_RETURN as it has been done before. All it takes is one transaction with an OP_RETURN output containing the information related to the documents proving possession of the thing in real world.
If I am not wrong there are limits of data in each OP_RETURN with the need of splitting the data in multiple transactions.
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Correct, one transaction only allow single OP_RETURN with maximum size 80 bytes. If you want to store more data, you either need to create multiple transactions or create non-standard transaction (size higher than 80 bytes and/or multiple OP_RETURN) and ask miner/pool to include it manually.