1. An information processing apparatus comprising: a processor configured to function as: an acquiring unit that acquires, for a plurality of documents, candidates for elements representing characteristics of each of the plurality of documents; an extraction unit that extracts, from the candidates acquired by the acquiring unit, common elements common to two or more of the plurality of documents; a selection unit that extracts, from the plurality of documents, a document including two or more common elements among the common elements, and determines the two or more common elements included in the extracted document to be elements representing characteristics of the document; a first acquiring unit that acquires, for each of the plurality of documents, a first group of elements included in a first image generated by reading the document; an addition unit that generates a plurality of second images by adding noises that differ from each other to the first image; a second acquiring unit that acquires second groups of elements included in the plurality of respective second images; and a first extraction unit that extracts, from the first group of elements, candidates for elements representing characteristics of the document in accordance with degrees of similarity between elements included in the first group of elements and elements included in the second groups of elements.