An image forming apparatus configured to communicate with an access rights management server that associates a document ID for an image file with information indicating operation rights of the image file and that manages said document ID, the image forming apparatus comprising: a storage unit for storing first image data, second image data and management information indicating at least information about an attribute of the second image data, the second image data being related to the first image data and being in a format different from the format of the first image data, wherein the first image data is capable of including the document ID managed by the access rights management server and if the first image data includes the document ID, the access rights management server is configured to associate the document ID with information indicating the operation rights of the first image data such that the access rights management server is configured to manage operation rights of the first image data, wherein the format of the second image data is not capable of including the document ID, such that operation rights of the second image data are not manageable by the access rights management server, and wherein the second image data has a format suitable for internal processing performed in the image forming apparatus, the first image data is generated by converting the second image data, and the second image data is stored on the image forming apparatus; a setting unit for making a setting that restricts the operation on the first image data by adding license information including a document ID to the first image data; and a restricting unit comprising an encrypting unit configured to encrypt the second image data, wherein the restricting unit is configured to restrict an operation on the second image data corresponding to the first image data to which a document ID has been added by encrypting the second image data and updating management information regarding the second image data related to the first image data to indicate that the second image data is encrypted. a storage unit for storing first image data, second image data and management information indicating at least information about an attribute of the second image data, the second image data being related to the first image data and being in a format different from the format of the first image data, wherein the first image data is capable of including the document ID managed by the access rights management server and if the first image data includes the document ID, the access rights management server is configured to associate the document ID with information indicating the operation rights of the first image data such that the access rights management server is configured to manage operation rights of the first image data, wherein the format of the second image data is not capable of including the document ID, such that operation rights of the second image data are not manageable by the access rights management server, and wherein the second image data has a format suitable for internal processing performed in the image forming apparatus, the first image data is generated by converting the second image data, and the second image data is stored on the image forming apparatus; a setting unit for making a setting that restricts the operation on the first image data by adding license information including a document ID to the first image data; and a restricting unit comprising an encrypting unit configured to encrypt the second image data, wherein the restricting unit is configured to restrict an operation on the second image data corresponding to the first image data to which a document ID has been added by encrypting the second image data and updating management information regarding the second image data related to the first image data to indicate that the second image data is encrypted.