Laminator pouches are designed to be used with a laminator which passes the pouch and its contents between heated rollers. These are sold by larger branches of Tesco, Sainsburys, etc (as well as discount stationers) for, typically, about �18.
I suppose you could try a 'DIY' approach. Lay the pouch, with its contents, on top of a firm smooth surface. Place a sheet of brown wrapping paper on top and then run a hot iron over everything. (NB: I've never tried this and I don't really recommend it but it might be worth a try if you don't want to fork out for a laminator. Just don't try it with an important document though!).
Chris