12. A document management apparatus for managing a correction history of a document, the apparatus comprising: a document management server controlled by a central processing unit; a document store section for storing the document; a correction history table store section for storing a correction history table; a document input section for accepting input of the document which is original and for storing the document inputted in the document store section; a document correction section for correcting a character string of the document stored in the document store section in response to operation input, for registering a correction history including a number of characters deleted by a character string deletion process and a correction history including a number of characters 5 before replacement by a replacement process in the correction history table, and for storing the corrected document in the document store section; and a correction history analysis section for referring to the correction history table to make a decision table including an opacity rate, the opacity rate obtained by dividing a total of the number of the characters deleted by the character string deletion process and the number of the characters before the replacement by the replacement process by a number of characters included in the original document.
12. A document management apparatus for managing a correction history of a document, the apparatus comprising: a document management server controlled by a central processing unit; a document store section for storing the document; a correction history table store section for storing a correction history table; a document input section for accepting input of the document which is original and for storing the document inputted in the document store section; a document correction section for correcting a character string of the document stored in the document store section in response to operation input, for registering a correction history including a number of characters deleted by a character string deletion process and a correction history including a number of characters 5 before replacement by a replacement process in the correction history table, and for storing the corrected document in the document store section; and a correction history analysis section for referring to the correction history table to make a decision table including an opacity rate, the opacity rate obtained by dividing a total of the number of the characters deleted by the character string deletion process and the number of the characters before the replacement by the replacement process by a number of characters included in the original document. 13. The document management apparatus according to claim 12 , wherein: the document correction section registers a correction history indicative of a character string deletion process, a character string addition process, and a character string replacement process performed on the document in the correction history table; and if a character string is added at a place where a character string is deleted, the document correction section recognizes that character string replacement is performed, and registers a correction history in the correction history table.