13. The information management system according to claim 9 , wherein the contents server is configured to: set, when a plurality of paper documents corresponding to the digital document exist, in case of which an attribute of any of the plurality of paper documents corresponding to the digital document is set to indicate a master of the document, an attribute of the digital document corresponding to the paper document to indicate that a change to the digital document is inhibited; and set, in case of which an attribute of none of the plurality of paper documents corresponding to the digital document is set to indicate a master of the document, the attribute of the digital document corresponding to the paper document to indicate a master of the document.
13. The information management system according to claim 9 , wherein the contents server is configured to: set, when a plurality of paper documents corresponding to the digital document exist, in case of which an attribute of any of the plurality of paper documents corresponding to the digital document is set to indicate a master of the document, an attribute of the digital document corresponding to the paper document to indicate that a change to the digital document is inhibited; and set, in case of which an attribute of none of the plurality of paper documents corresponding to the digital document is set to indicate a master of the document, the attribute of the digital document corresponding to the paper document to indicate a master of the document. 15. The information management system according to claim 13 , wherein the contents server generates a screen which displays information as to the digital document, information as to the plurality of paper documents, and information as to which one of the digital document and the plurality of paper documents is the master of the document.