One of the oldest forms of relief printing, Letterpress is a technique where a design forms an inked impression onto paper. With this process, the inks are opaque and are handled one at a time.
Similar to Letterpress, Foil Stamping forms a debossed texture of the design into the paper. Unlike letterpress, the machine heats a copper plate to press foil into the paper. The foil is not opaque, so paper colors will not show through.
Essentially, duplexing is when one paper glues to another. This process is how a piece of stationery can have different colored fronts and backs. Or, duplexing can stick two of the same papers together for a thicker piece of stationery.
A fun pop of detail for any piece of stationery is edge painting. This process adds color or foil to the outer edges around a piece of paper.