Geschke set up Adobe in 1982, giving the world the ubiquitous PDF software, among many other audio-visual innovations.
He made headlines 10 years later when he was kidnapped at gunpoint and held for ransom before being released unhurt after a four-day ordeal.
Geschke died in California on Friday.
Geschke and Warnock were responsible for transformative software inventions, including PDF, Acrobat, Illustrator, Premiere Pro and Photoshop.
In 2009, President Barack Obama awarded Geschke and Warnock the National Medal of Technology. "He was really a humble, humble man – I can say that, as his wife," Nan Geschke told Mercury News.