A server comprising: a first acquisition unit configured to acquire workflow definition information indicating a workflow selected according to a user operation from among a plurality of workflows, the workflow defining a plurality of processes in a predetermined order; a communication unit (250, 2005) configured to receive, from an image forming apparatus, image data generated by reading a document and a size of the image data; a control unit (220, 2000) configured to execute processing on the received electronic document image data according to the workflow defined by the workflow definition information; a second acquisition unit (221, 2000) configured to obtain a first size of the data after a specific process of the plurality of processes is performed on the data, and a storage unit (243, 2004) configured to store the first size obtained with the second acquisition unit, wherein the control unit (220, 2000) performs a subsequent process on the data based on the first size of the data, the subsequent process being one of a plurality of subsequent processes each of which is defined as a process subsequent to the specific process in the workflow definition information, and characterized in that the workflow contains a plurality of specific processes, the second acquisition unit (221, 2000) obtains the size of the data each time one of the plurality of specific processes is performed according to the workflow, and updates the first size stored in the storage unit (243, 2004) each time the size is obtained, and when the second acquisition unit obtains, in response to a second specific process being executed, a size of the data, and updates the first size stored in the storage unit with the size obtained after the second specific process, the control unit performs a third process subsequent to the second specific process dependent upon the updated size of data stored in the storage unit; wherein the specific processes are processes able to change the size of the data. a first acquisition unit configured to acquire workflow definition information indicating a workflow selected according to a user operation from among a plurality of workflows, the workflow defining a plurality of processes in a predetermined order; a communication unit (250, 2005) configured to receive, from an image forming apparatus, image data generated by reading a document and a size of the image data; a control unit (220, 2000) configured to execute processing on the received electronic document image data according to the workflow defined by the workflow definition information; a second acquisition unit (221, 2000) configured to obtain a first size of the data after a specific process of the plurality of processes is performed on the data, and a storage unit (243, 2004) configured to store the first size obtained with the second acquisition unit, wherein the control unit (220, 2000) performs a subsequent process on the data based on the first size of the data, the subsequent process being one of a plurality of subsequent processes each of which is defined as a process subsequent to the specific process in the workflow definition information, and characterized in that the workflow contains a plurality of specific processes, the second acquisition unit (221, 2000) obtains the size of the data each time one of the plurality of specific processes is performed according to the workflow, and updates the first size stored in the storage unit (243, 2004) each time the size is obtained, and when the second acquisition unit obtains, in response to a second specific process being executed, a size of the data, and updates the first size stored in the storage unit with the size obtained after the second specific process, the control unit performs a third process subsequent to the second specific process dependent upon the updated size of data stored in the storage unit; wherein the specific processes are processes able to change the size of the data.