13. A document processing method, comprising the steps of: (a) acquiring document data; (b) extracting character strings that correspond to at least one of a heading, a title, or a subtitle as bookmark candidate character strings from the acquired document data; (c) deriving respective features of the extracted bookmark candidate character strings, and categorizing said bookmark candidate character strings having a common feature into one group and creating a format for the group based on the common feature of the group; (d) displaying said extracted bookmark candidate character strings in a list form, and displaying the format corresponding to said bookmark candidate character strings; (e) correcting the format in response to receiving a correcting operation given to the displayed format from a user; (f) when the format is corrected, extracting the character strings again that have the common featured of the corrected format from the acquired document data as said bookmark's candidate character strings; and (g) generating bookmark data based on said character strings extracted from the acquired document data and adding the generated bookmark data to the acquired document data.
13. A document processing method, comprising the steps of: (a) acquiring document data; (b) extracting character strings that correspond to at least one of a heading, a title, or a subtitle as bookmark candidate character strings from the acquired document data; (c) deriving respective features of the extracted bookmark candidate character strings, and categorizing said bookmark candidate character strings having a common feature into one group and creating a format for the group based on the common feature of the group; (d) displaying said extracted bookmark candidate character strings in a list form, and displaying the format corresponding to said bookmark candidate character strings; (e) correcting the format in response to receiving a correcting operation given to the displayed format from a user; (f) when the format is corrected, extracting the character strings again that have the common featured of the corrected format from the acquired document data as said bookmark's candidate character strings; and (g) generating bookmark data based on said character strings extracted from the acquired document data and adding the generated bookmark data to the acquired document data. 18. The document processing method according to claim 13 , wherein the features of each of said character strings derived in said step (c) include an attribute contained in the character string.