A Python script to merge every two pages of a PDF file into one page

merge.py

# pip install PyMuPDF
# usage: python merge.py input_file.pdf

import sys

import fitz


def merge_pages(input_file, output_file):
    with fitz.open(input_file) as doc:
        new_doc = fitz.open()
        for i in range(0, doc.page_count, 2):
            page_rect = doc[i].rect
            rect = fitz.Rect(0, 0, page_rect.width, page_rect.height)
            new_page = new_doc.new_page(width=rect.width, height=rect.height * 2)
            new_page.show_pdf_page(rect, doc, i)
            if i + 1 < doc.page_count:
                rect = fitz.Rect(
                    0, doc[i].rect.height, page_rect.width, page_rect.height * 2
                )
                new_page.show_pdf_page(rect, doc, i + 1)
        new_doc.save(output_file)


if __name__ == "__main__":
    try:
        input_file = sys.argv[1]
    except IndexError:
        print("Usage: python merge.py input_file.pdf")
        sys.exit(1)
    if not input_file.endswith(".pdf"):
        print("Input file must be a PDF file")
        sys.exit(1)
    output_file = input_file[:-4] + "_merged.pdf"
    merge_pages(input_file, output_file)