Split pdf pages wich contains slides so that every page contains just one slide. It only works with two slides per page, either horizontal or vertical.

split.py

#!/usr/bin/env python

# Based on http://unix.stackexchange.com/a/12483
# To use it you have to give it execution privilleges
# with the command:
#   chmod u+x split.py
# Then you can use it like this:
#   ./split.py <slides.pdf >split.pdf
import copy, sys
from pyPdf import PdfFileWriter, PdfFileReader
input = PdfFileReader(sys.stdin)
output = PdfFileWriter()
for p in [input.getPage(i) for i in range(0,input.getNumPages())]:
    u = copy.copy(p)
    d = copy.copy(p)
    (xur, yur) = p.mediaBox.upperRight
    (xll, yll) = p.mediaBox.lowerLeft

    if xll > yll:
        # horizontal
        u.mediaBox.upperRight = (xur/2, yur)
        d.mediaBox.lowerLeft = (xur/2, yll)

    else:
        # vertical
        u.mediaBox.lowerLeft = (xll, yur/2)
        d.mediaBox.upperRight = (xur, yur/2)

    output.addPage(u)
    output.addPage(d)
output.write(sys.stdout)