Linking product with file bigger than 2MB limit

hi,

as the title says, i wanted to link a product with a large file, sometimes bigger than 500mb, but since the upload limit is 2mb, the upload process obviously failed. i tried to manually link the file with the product but ended up messing the code, so i wondered if linking manually is even possible, and if so, would you kindly tell which code of which file should i alter. thanks nicholas for your hard work.