from pyPdf import PdfFileWriter, PdfFileReader

output = PdfFileWriter()
input = PdfFileReader(open("input.pdf", 'rb'))

for x in xrange(input.numPages):
    page = input.getPage(x)
    box = page.mediaBox
    
    box.upperLeft = (box.getUpperLeft_x() / 1.1, box.getUpperLeft_y() / 1.1)
    box.lowerLeft = (box.getLowerLeft_x() + 50, box.getLowerLeft_y() + 50)
    
    output.addPage(page)

output.write(open("output.pdf", "wb"))