I'm not sure what a maxpedition pack is, but if you go to grangersusa.com, and click on waterproofing, you can find some stuff to waterproof nylon. I bought the wash-in waterproofing stuff and the g-wash cleaner. The g-wash cleaner cleans the material without removing existing waterproofing and doesn't leave any detergent or residue that might interfere with the adherence of their waterproof formulas. I used the solutions to waterproof a jacket that I use in the rain a lot, a pair of snowboard pants, and for an E-Tech Explorer laptop backpack. They work pretty well, but might be expensive, and are only good for waterproofing 3 garments. I think I paid about 24 dollars for both of them from REI. I bought them on the website and had them shipped to my local REI for pickup to avoid shipping costs. The waterproofing is activated by the heat of the clothes dryer. I'm not sure if they're all activated this way. I know there are a few different ones they sell.