Bread flour contains about two percent more protein than all-purpose flour; the extra protein content affects the structure and texture of the bread. If you find that you do not have enough bread flour for a recipe, substitute all-purpose flour for the remainder of the bread flour. Make a few adjustments to the recipe so your mixture of flours will achieve the same results as using all bread flour.
Use unbleached all-purpose flour if you can -- it has a slightly higher protein content than bleached flour.
Add an extra tablespoon of flour for each cup of all-purpose flour you use in place of bread flour.
Add 1 tsp. of vital wheat gluten and 1 1/4 tsp. water for each cup of all-purpose flour to obtain a chewier texture.