The biggest value of the manual is the sequences. Most people quit Ashtanga because they don't have 90 minutes to do the Full Primary.
I understand the temptation of a free PDF — budgets are tight. If you truly cannot afford the book, consider this: borrow a copy from a fellow yogi, request it from your public library (they can often interlibrary loan it), or save up slowly. Checking a PDF to learn the sequence is better than nothing, but if the book changes your practice, honour that by eventually buying a copy. ashtanga yoga the practice manual david swenson pdf