While many users search for a "pdf gratis google drive" version, it is important to note that the physical book published by Seigensha Art Publishing is a copyrighted work. However, the creative community has built several legal, open-source tools to interact with Wada's palette:
To get the PDF, your best bet is to search the Internet Archive or check if your local/school library offers a digital loan. The modern physical version (published by Seigensha) is highly recommended if you need a permanent reference copy.