If you've got a big paper pasting project going on (large group collage project, science fair display poster, etc) it is much easier and cheaper to cook this up rather than use white glue or rubber cement.
1/3 cup flour (all purpose white flour or bread making flour are best)
2 tbsp sugar
1 cup water
1/2 tsp alum powder (optional preservative -- not necessary if the glue is for immediate use)
Mix flour and sugar. Gradually add water while stirring vigorously to prevent lumps.
Cook over low heat, stirring constantly, till the paste is clear. Remove from heat and stir in the optional alum.
Spread over paper or cardboard with a paintbrush. Press and smooth paper to be glued before the paste dries.
Store in a covered glass jar. This will keep for several weeks without refrigeration.