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. 11. The apparatus according to claim 7 , further comprising: a storage unit to store the generated key index in an image file format separately from the scanned document, or in a header area of the scanned document in an image file format.