How can I replace a color in a finished PDF file?

I'm on Mac 10.9.2 Mavericks and I want to print a PDF file made by someone else, composed of Powerpoint slides. The problem is, all pages have a standard layout where there are giant cyan lines on the bottom, without any text on them other than page numbers, like so:

http://i.gyazo.com/d82c816638e27f82e3978fc8a3c6e67e.png

How can I turn these cyan parts white, WITHOUT cropping?