The use of a blockchain is for proof of publication, not storage of the publications. It doesnt make sense, nor is it desirable. The blockchain means you can prevent people from cheating. For example, I heard the US Supreme Court has rulings which only exist in their library... and have been altered after the fact. So notarizing PDF versions of these for example would mean you can always check the authenticity of the document and that it hasnt been changed.

When decentralized storage solutions are finally solved, like MAIDSafe then I would extend the protocol to have resource pointers so the actual documents can exists "in the cloud" too.  Remember in many cases it's not even desirable to reveal what you are notarizing: imagine you made a new technology design. You want to work on it in secret, but also prove you were the first. You can ensure you retain that proof without publishing the design to the world, yet, you can prove it after the fact if the need arrives. At that point you would have to reveal the document.

Once there are libraries for zero-knowledge proofs, you could then go a step further and notarize the snark and never have to reveal the document since the snark can do the proof using "moon maths".