8. A document editing apparatus for editing an electronic document including a plurality of hierarchically arranged objects, comprising: a storage to store an original electronic document including the hierarchically arranged objects representing one of a text, an image, a drawing, and a table; and a processor, the processor configured to: extract an object to be masked in an area specified by a user from the original electronic document stored in the storage; determine whether the extracted object is superimposed by the user specified area serving as a masking area of a target document input by a user; convert, into different information, information included in an area of the object determined to be superimposed by the user specified area to generate a processed electronic document; and store the processed electronic document in the storage.
8. A document editing apparatus for editing an electronic document including a plurality of hierarchically arranged objects, comprising: a storage to store an original electronic document including the hierarchically arranged objects representing one of a text, an image, a drawing, and a table; and a processor, the processor configured to: extract an object to be masked in an area specified by a user from the original electronic document stored in the storage; determine whether the extracted object is superimposed by the user specified area serving as a masking area of a target document input by a user; convert, into different information, information included in an area of the object determined to be superimposed by the user specified area to generate a processed electronic document; and store the processed electronic document in the storage. 14. The document editing apparatus according to claim 8 , wherein the processor is further configured to display, in an identifiable fashion, a converted part of the information included in the area of the object determined to be superimposed by the user specified area.