mix two pdfs with odd and even pages from a document feeder scanner

pdfmix.py

#!/usr/local/bin/python

from PyPDF2 import PdfFileReader, PdfFileWriter
import sys

if len(sys.argv) < 4:
  print "usage: mix.py odd.pdf even.pdf result.pdf"
  exit()

odd = PdfFileReader(open(sys.argv[1],'rb')).pages
even = PdfFileReader(open(sys.argv[2],'rb')).pages

if (len(odd) - len(even) > 1) or (len(odd) < len(even)):
  print "document length must match or even document must be one page less"
  exit()

writer = PdfFileWriter()

for n in range(0,len(odd)):
  writer.addPage(odd[n])
  if n < len(even):
    writer.addPage(even[-(n+1)])

writer.write(open(sys.argv[3], 'wb'))

you will need a pip install pypdf2