merge-pdf.py

from PyPDF2 import PdfWriter
import os
#https://pypdf2.readthedocs.io/en/3.0.0/user/merging-pdfs.html

merger = PdfWriter()

os.chdir("/Users/rcharanthara/Downloads/")
input1 = open("1.pdf", "rb")
input2 = open("2.pdf", "rb")
input3 = open("3.pdf", "rb")
input4 = open("4.pdf", "rb")

# add the first 3 pages of input1 document to output
merger.append(fileobj=input1, pages=(0, 1))

# insert the first page of input2 into the output beginning after the second page
merger.merge(position=2, fileobj=input2, pages=(0, 1))

merger.merge(position=3, fileobj=input3, pages=(0, 1))

# append entire input3 document to the end of the output document
merger.append(input4)

# Write to an output PDF document
output = open("document-output.pdf", "wb")
merger.write(output)

# Close File Descriptors
merger.close()
output.close()