A one-way link (data diode) transmits it to a box with simplified hardware (eg RISC architecture). The box has a dedicated monitor and keyboard. Once you're finished, you sell the box on Craiglist. Then, buy a new, sealed replacement from Best Buy.

Pay per view was an expensive, business model for cable. For PDF's, it's even more expensive.

Note: It's more convenient than full, per-app, physical security.