7. The document processing apparatus according to claim 1 , further comprising: a filter storing unit configured to store a plurality of filters associated with application programs, respectively; and a filter selecting unit configured to select a filter associated with the first application program from the filter storing unit, wherein the character string extracting unit is configured to detect the one or more character strings using the filter selected by the filter selecting unit.
7. The document processing apparatus according to claim 1 , further comprising: a filter storing unit configured to store a plurality of filters associated with application programs, respectively; and a filter selecting unit configured to select a filter associated with the first application program from the filter storing unit, wherein the character string extracting unit is configured to detect the one or more character strings using the filter selected by the filter selecting unit. 8. The document processing apparatus according to claim 7 , wherein the character string extracting unit is configured to collect the one or more character strings detected from the document file having the content displayed on the first screen and to create a list file in which the one or more character strings are described in a predetermined description format which can set element names for the character strings.