This document discusses using QR codes in outdoor advertising. It notes that QR codes work best when accessible to pedestrian traffic in locations like airports, malls, and transit. The size of the QR code should be dependent on the proximity and viewing angle, and can be as large as the entire display. Testing different QR code locations, sizes, and colors is recommended. QR codes can link to URLs, PDFs, social media, and allow for call-to-actions. Metrics can also be tracked from QR code usage in outdoor advertising. The document provides contact information for representatives from Cloud Four, LynkSnap, and Clear Channel Outdoor to answer questions.