1. An image processing device, comprising: a processor that executes: an input part for inputting image data; a word extracting part for extracting a word from texts contained in said image data; a synonym obtaining part for obtaining a synonym corresponding to said word, and for associating said obtained synonym with said word; a position identifying part for identifying a display position on said image data of said word with which said synonym is associated; a layer creating part for creating an accompanying layer to add to an original layer, which is said image data containing said word, and for embedding said synonym associated with said word within a position on said accompanying layer that is the same as the display position of the word in said original layer identified by said position identifying part so that the synonym in the accompanying layer overlaps the word in the original layer without replacing the word in the original layer, wherein the location of a first character of the synonym in the accompanying layer matches the location of a first character of the word in the original layer, or the display area of the synonym in the accompanying layer has the same size as the display area of the word in the original layer and is at the same location in the accompanying layer as the display area of the word in the original layer; and an output image generating part for generating output image data including said original layer containing said word and said accompanying layer within which said synonym is embedded and overlaps the word.