You can find manuals for Canon printers, including the MX340 model, on Canon's website, Canon.com. The product page for the MX340 includes a link to Brochures & Manuals, where you can find the user manual, an introductory guide for those just getting started with the printer and a troubleshooting manual.
Canon primarily designs and produces imaging equipment for businesses and consumers. Canon's product line includes printers, fax machines, cameras, lenses and projectors, as well as radiology machines and semiconductors. The first Canon office in the United States opened in New York in 1955, and Canon U.S.A. operates over 21 offices in the country as of 2015.