PDFのフォントを書き換えたい

import fitz  # PyMuPDF
from reportlab.pdfbase import pdfmetrics
from reportlab.pdfbase.ttfonts import TTFont
from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import letter, A4
from reportlab.pdfbase.cidfonts import UnicodeCIDFont

# 日本語フォントの登録
pdfmetrics.registerFont(TTFont("BIZ-UDGOTHICR", r"C:\WINDOWS\Fonts\BIZ-UDGOTHICR.TTC"))
pdfmetrics.registerFont(UnicodeCIDFont("HeiseiKakuGo-W5"))

# PDFファイルを開く
input_pdf_path = "input.pdf"
doc = fitz.open(input_pdf_path)

# 新しいPDFを作成
output_pdf_path = "output.pdf"
c = canvas.Canvas(output_pdf_path, pagesize=A4)

for page_number in range(len(doc)):
    page = doc.load_page(page_number)
    text_instances = page.get_text("dict")["blocks"]

    for instance in text_instances:
        if instance["type"] == 0:  # テキスト
            for line in instance["lines"]:
                for span in line["spans"]:
                    x, y = span["bbox"][0], span["bbox"][3]
                    text, size = span["text"], span["size"]

                    # 日本語フォントを使用
                    # c.setFont('HeiseiKakuGo-W5', size)
                    c.setFont("BIZ-UDGOTHICR", size)

                    c.drawString(x, 841.89 - y, text)  # y座標の調整
        elif instance["type"] == 1:  # 画像
            x0, y0, x1, y1 = instance["bbox"]
            matrix = fitz.Matrix(300 / 72, 300 / 72)  # 解像度を300 DPIに設定
            pix = page.get_pixmap(clip=fitz.Rect(x0, y0, x1, y1), matrix=matrix)
            img_file = f'tmp_image/tmp_image{page_number}_{instance["number"]}.png'
            pix.save(img_file)
            c.drawInlineImage(
                img_file, x0, 841.89 - y1, width=x1 - x0, height=y1 - y0
            )  # y座標の調整

    c.showPage()

c.save()