7. A document processing apparatus, comprising: a symbol-related information acquirement unit to identify a text area from a scanned document, extract symbols from the identified text area, and acquire symbol-related information regarding each extracted symbol; a symbol division unit to divide the extracted symbols into a plurality of groups based on a preset reference value regarding the symbol-related information; and a key index generation unit to generate a key index by arranging one group of symbols from among the divided groups, wherein the symbol-related information is information regarding at least one of height, width, and stroke width of the corresponding extracted symbol.
7. A document processing apparatus, comprising: a symbol-related information acquirement unit to identify a text area from a scanned document, extract symbols from the identified text area, and acquire symbol-related information regarding each extracted symbol; a symbol division unit to divide the extracted symbols into a plurality of groups based on a preset reference value regarding the symbol-related information; and a key index generation unit to generate a key index by arranging one group of symbols from among the divided groups, wherein the symbol-related information is information regarding at least one of height, width, and stroke width of the corresponding extracted symbol. 8. The apparatus according to claim 7 , wherein the symbol division unit divides the extracted symbols into several groups based on a first reference value indicating a sum of the height and width of the corresponding extracted symbol, and a second reference value indicating the stroke width of the corresponding extracted symbol.