A bootleg PDF of an outdated edition might save you $50 today, but it will cost you in frustration (bad scans, missing audio examples, and obsolete transposition keys). The wisest investment is to purchase a (available for as little as $15 on AbeBooks or eBay) or rent the 6th edition ebook legally.
You are not alone in looking for a free PDF. Textbook costs are high—the 6th edition retails for around $100-$150 new. As a result, many students try to locate a scanned copy of an older edition (e.g., 3rd or 4th) online.