In a large bowl, sift together flour, cocoa powder, cinnamon, and salt. Set aside.
In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar on medium speed until light and fluffy, about 2 minutes. Beat in eggs and vanilla.
Add dry ingredients; mix on low speed until thoroughly combined. Divide dough in half, and wrap in plastic. Chill for at least 1 hour.
Preheat oven to 350 degrees. On a lightly floured surface, roll out dough a 1/8-inch-thickness. Cut into desired shapes. Transfer to ungreased baking sheets; refrigerate until firm, 15 minutes. Bake until crisp but not darkened, 8 to 10 minutes. Transfer to a wire rack to cool completely; decorate as desired.