def pdf_qa_baseline(
    pdf_path: str,
    question: str,
    top_k: int = 3,
    annotate_pdf: str | None = None,
):
    # 1. Parsing
    line_df = fitz_pdf_to_line_df(pdf_path)

    # 2. Retrieval
    page_df = embed_page_df(build_page_df(line_df))
    _, filtered = retrieve_pages(page_df, line_df, question, top_k)

    # 3. Generation
    answer = llm_answer_with_evidence(question, filtered)

    # 4. Optional highlighting on the source PDF
    if annotate_pdf is not None:
        passage = passage_lines_df_from_answer(line_df, answer)
        bboxes = passage_bbox_by_page(passage)
        draw_passage_rectangles(pdf_path, bboxes, annotate_pdf)

    return answer