1. A method of scanning a document, comprising: obtaining an original image by scanning a document, the document including: a plurality of selectively identifiable areas having respective images, and at least two pairs of marks, the at least two pairs of marks including a first pair of marks defining a size of at least one of the selectively identifiable areas and a second pair of marks defining a size of at least another one of the selectively identifiable areas; measuring a slope of the original image based on slopes of objects other than the at least two pairs of marks included in at least one of the selectively identifiable areas; rotating the original image based on the measured slope; and after the original image is rotated, detecting the first and second pair of marks included in the rotated original image; extracting a first image of a first area defined by the detected first pair of marks from the rotated original image and a second image of a second area defined by the detected second pair of marks from the rotated original image; and creating a new document file based on at least one of the extracted first and second images.