To produce accurate editing results, the ambiguity of editing scopes related to marked correction signs should be solved. Proofreading the web document modifies the document structures, and the modified structures should be robustly valid for the defined DTD. This paper presents a pen-based proofreading interface in the XML document. In the proposed interface, correction signs are free-drawn, and the editing scopes are recognized and revised based on the contexts of the document to minimize the ambiguity of the editing scopes. The proposed interface provides both implicit and explicit modification methods for document structures. As a result, the editing scopes processed in the proposed interface are more accurate, and the document structures are maintained valid for DTD after the editing.