A digital signature disallows alteration of the document. Appropriate alterations, however, should be allowed for some signed documents in practical use because of security requirements other than the integrity of the document. For example, when administrative documents are disclosed, based on the information disclosure law, in such documents, sensitive information, such as privacy information or national secrets is masked in advance. If this procedure is applied using existing digital signature technologies, the original digital signature becomes invalid when part of the document is sanitized. This problem is called the digital document sanitization problem and digital document sanitization schemes have been proposed as a solution to this problem. However, these schemes have disadvantages, such as a lack of flexibility in selecting sanitization blocks or inability to detect illegal sanitization by the sanitizer. In the present paper, we propose a digitally signed document flexible sanitizing scheme (DDFS) that can answer requests for flexible changes in the sanitized sections of a document without compromising security.