1. A document processing system for processing a hand-written first document on a sheet, said document processing system comprising: an encoding unit configured to encode a sheet ID for identifying the first document to generate a coded sheet ID; a decoding unit configured to decode the coded sheet ID; a document-sheet ID association unit configured to associate the sheet ID with a document ID assigned to a computerized second document; a printing unit configured to acquire the sheet ID and print the coded sheet ID on the first document; a sheet ID management unit configured to manage the sheet ID; an information acquisition unit configured to acquire the sheet ID decoded by the decoding unit, and hand-written data from the first document on which the coded sheet ID is printed; and a process-sheet ID association unit configured to associate the sheet ID with a process ID of a process for processing the hand-written data acquired by the information acquisition unit.