John Warnock, who invented the PDF and co-founded Adobe Systems, has died. He was 82. The Silicon Valley entrepreneur and computer scientist died Saturday surrounded by family, Adobe said in a statement. The company didn't give a cause of death or say where Warnock died.“John’s brilliance and innovations left an indelible mark on Adobe, the technology industry and the world,” Adobe said. Warnock worked for Xerox before he and colleague Charles Geschke created a company around a rejected idea in 1982. Nearly a decade later, Warnock outlined an early version of the Portable Document Format, or PDF, transforming the way...