1. An electronic document generation system comprising: an image forming apparatus configured to generate a scanned image of an original document; and an external terminal configured to generate an electronic document on the basis of image data regarding the scanned image received from the image forming apparatus, the image forming apparatus including: an auxiliary data generation unit configured to generate auxiliary data that is used in processing for generating the electronic document; and a communication unit configured to transmit the auxiliary data to the external terminal, and the external terminal including: a reception unit configured to receive the auxiliary data from the image forming apparatus; and a document generation unit configured to use the auxiliary data to generate the electronic document on the basis of the image data regarding the scanned image in cooperation with an external cooperative device that is a different device from the external terminal, the document generation unit being configured to complement a result of processing performed on the image data with the auxiliary data to generate the electronic document.