QR codes are great for augmenting ads, booklets and other stuff, but if you want reliable readability, you shouldn't go with more than a simple color change, in my experience.<p>I was tasked with creating QR codes for certificates (every certificate leads to a unique page for the certificate number on the website, for security and more information since the certificates were small and made to be pretty instead of useful).<p>We ended up with Level M golden (more like dark yellow) colored QR codes in the corner - using higher error correction is actually detrimental the smaller you go, and backgrounds, embossing or any kind of advanced design would lead to it being very hard to read - it's better to have a plain ugly QR code that is immediately scannable with any device than a pretty one that is unreadable (just imagine your buyers trying to scan the damn thing five times in a row then give up in frustration).<p>But the client really liked the idea (and the results), and I am still surprised that so many people don't even consider this nowadays...