But in 1992, they dropped the sequel: .
No. The book is still under copyright (Giger died in 2014, and his estate is very active). Any site offering a “free download” is either a virus, a scanned copy missing 30 pages, or bait to steal your credit card info.
Necronomicon II is a ghost. You can spend hours chasing a broken PDF link, or you can spend that time hunting down a real copy.