https://smashmockup.com/us-letter-brochure-cover-mockup-with-shadow-overlay/

Free US Letter brochure cover and back cover mockup with 3 styles of shadows overlay which you can apply instantly for a beautiful realistic final rendering. 

All are easy to customize using smart objects to add your cover and back cover designs. Then you can apply the shadow overlays simply by showing or hiding the shadow layers and adjusting their opacity.

This fully layered PSD file allows you to show off your design. The PSD file allows you to change all elements and come with many customization options. Completely layered file with smart object.