Embodiments of the disclosed innovations provide systems and methods for automatically locating and retrieving digital supplemental materials and counterparts of rendered documents. These systems and methods are especially useful when the provider or copyright holder of the digital document charges a fee for access to the digital materials. Some embodiments solve the technical problem of allowing a user to access restricted digital content associated with a rendered document via a search string captured from the rendered document. Some embodiments further provide automatic intermediation to gain access to protected digital materials.