I'm a professional photographer and I'm 100 percent serious. Try taking a photo of any random poster you have lying around and try to match the foreground and background image quality, then try to get your poster edges as perfectly straight. Also they don't sell this poster -- you'd have to find a super high-tes image then find a full-bleed large-format printer to print it on yourself, then hope there's no loss in quality, curling, etc. This image looks like OP took the digital file and dropped it on a protest photo in Photoshop. It's way too perfect. I'm open to other possibilities if you can explain how the shot was captured in a way that makes logical technical sense though.