Because George Ohsawa’s work is considered an "alternative health system" (not mainstream medicine), enforcement of digital copyright is very lax. However, the non-profit GOMF relies on PDF sales to keep translating his unpublished Japanese works. If you find a free PDF, consider it a "preview" and donate or purchase a legal copy later.
Whether you find You Are All Sanpaku on a dusty bookshop shelf or as a scanned PDF on your tablet, the message is the same: You are the master of your health. The yin and yang are in your bowl of rice.