another way is to open the envelope, take out all paperwork, stuff all paperwork into the self addressed stamped envelope envelope with postage already paid, and send back to company;

I write "NO THANKS" in bold Sharpie on the application and mail it along with the envelope it came in (and sometimes other junk mail for added weight) and mail it back to them in their own postage paid envelope. This they they can pay the postage on their own junk mail and the Postal Service gets paid.