6. The method according to claim 4 , further comprising notifying presence of the related document data specified in the specifying step, in response to an input of document data in the scanning step.
4. A document processing method of a document processing system having a storage unit for storing a plurality of items of document data, the method comprising: receiving document data via a network; scanning a document and inputting document data of the document; analyzing the document data input in the scanning step and extracting content data embedded in the input document data; determining whether the document data is received in the receiving or the document data is input in the scanning step; specifying, in a case where it is determined that the document data is received in the receiving step, based on meta data of the document data, related document data related to the received document data among the plurality of items of document data stored in the storage unit, and specifying, in a case where it is determined that the document data is input in the scanning step, based on the content data extracted in the analyzing step, related document data related to the document data input in the scanning step among the plurality of items of document data stored in the storage unit; and controlling to store, in the storage unit in a case where it is determined that the document data is received in the receiving step, relation information representing a relation between the document data received by the receiving step and the related document data specified by the specifying step, and controlling to store, in the storage unit in a case where it is determined that the document data is input in the scanning step, relation information representing a relation between the document data input in the scanning step and the related document data specified in the specifying step, wherein at least one of the receiving step, the scanning step, the analyzing step, the specifying step and the controlling step is performed by using a processor and a memory.