Cuts cards out of a pdf page

cardcutter.py

from PyPDF2 import PdfWriter, PdfReader
from pdf2image import convert_from_bytes
from copy import deepcopy
import io
num = 1
reader = PdfReader("cards_no-borders.pdf")

for iter_page in reader.pages:
    for x in range(3):
        for y in range(3):
            
            writer = PdfWriter()
            page = deepcopy(iter_page)

            height = float(page.mediabox.height)
            width = float(page.mediabox.width)
            page.mediabox.upper_left = (
                float(page.mediabox.left) + x*width/3,
                float(page.mediabox.top) - y*height/3
            )

            page.mediabox.upper_right = (
                float(page.mediabox.left) + (width/3),
                page.mediabox.top
            )
            page.mediabox.lower_right = (
                page.mediabox.right,
                float(page.mediabox.bottom) + ((2-y)*(height/3))
            )
            writer.add_page(page)
            pdf_bytes = io.BytesIO()
            writer.write(pdf_bytes)
            pdf_bytes.seek(0)
            images = convert_from_bytes(pdf_bytes.read())
            filename = "cards/card%d.png"%num 
            images[0].save(filename, 'PNG')

            pdf_bytes.flush()
            num+=1