A blue penciler is a term that refers to an editor or a person who edits text. However, there are several synonyms for the word blue penciler that can be used interchangeably. The first one is a copy editor, which is a person who edits a writer's draft for errors, readability, and format. Another synonym is a proofreader, someone who reviews text for grammatical errors, spelling mistakes, and typos. In addition, a line editor is someone who reviews text at a more in-depth level, checking for consistency, pacing, and tone. Lastly, a content editor is someone who not only edits text but also assesses its overall structure, flow, and coherence. Regardless of the synonym used, the ultimate goal is to improve the quality of the written work.