OPEL KADETT OWNER'S MANUAL Pdf Download. View and Download Opel Kadett owner's manual online. Opel Kadett. Kadett Automobile pdf manual download. Opel Kadett Workshop & Owners Manual | Free Download Opel Kadett. The Opel Kadett is a small family car designed and produced by the German automanufacturer Opel since 1937. The first Opel car to carry the Kadett name was presented to the public in December 1936 by Opel's Commercial-Technical director, Heinrich Nordhoff, who would in later decades become known for his leadership role in building up the Volkswagen company.