A system is provided for processing a manual such as a maintenance manual of an airplane into a customized manual to provide a user with the manual. The document processing unit inserts insertion data in a manual document by referring to a manufacturer's additional dictionary, a user's additional dictionary, and a translation sentence insertion dictionary. Also, the data conversion unit implements a predetermined processing such as providing a layout to the manual document. Thereby, the system provides a manual of which contents and format are customized to a user company, in either electronic or paper-printed information.