What will happen to my chocolate chip cookies if I add more or less flour than the recipe calls for? 
A general answer, because a concise answer would need an entire recipe.  (all ratios that follow are by weight not volume measures)  Flour gives the cookie structure. The commonly followed ratio is:     Cookie dough = 3 parts flour, 2 parts fat, 1 part sugar   That 3:2:1 ratio results in the most common cookie texture.  Adding more flour give you a hard cookie like: ginger snaps, short bread, etc.  Reducing the flour, like a 1:1:1  flour-fat-sugar will give a drop cookie and often chewy.  I Googled, and found this informative piece How to Invent a Cookie Recipe. 