Cropping pages of a .pdf file

I was wondering if anyone had any experience in working programmatically with .pdf files. I have a .pdf file and I need to crop every page down to a certain size.

After a quick Google search I found the pyPdf library for python but my experiments with it failed. When I changed the cropBox and trimBox attributes on a page object the results were not what I had expected and appeared to be quite random.

Has anyone had any experience with this? Code examples would be well appreciated, preferably in python.

Answer

pyPdf does what I expect in this area. Using the following script:

#!/usr/bin/python
#

from pyPdf import PdfFileWriter, PdfFileReader

with open("in.pdf", "rb") as in_f:
    input1 = PdfFileReader(in_f)
    output = PdfFileWriter()

    numPages = input1.getNumPages()
    print "document has %s pages." % numPages

    for i in range(numPages):
        page = input1.getPage(i)
        print page.mediaBox.getUpperRight_x(), page.mediaBox.getUpperRight_y()
        page.trimBox.lowerLeft = (25, 25)
        page.trimBox.upperRight = (225, 225)
        page.cropBox.lowerLeft = (50, 50)
        page.cropBox.upperRight = (200, 200)
        output.addPage(page)

    with open("out.pdf", "wb") as out_f:
        output.write(out_f)

The resulting document has a trim box that is 200×200 points and starts at 25,25 points inside the media box. The crop box is 25 points inside the trim box.

Here is how my sample document looks in acrobat professional after processing with the above code:

This document will appear blank when loaded in acrobat reader.