The fundamental and applied engineering issues to develop stable and functional bioactive papers for health and environmental diagnostics are investigated. Enzymes are directly physisorbed on paper or retained on paper with a polymer. The reactivity and the thermal stability of enzymatic papers are quantified using an advanced colorimetric technique. Paper bioassays to identify antigens and antibodies in a biofluid, such as blood, are investigated. The blood typing using a low cost paper diagnostic is shown. The feasibility of thermal ink jet printing is illustrated for the precise deposition of biomolecules on paper and polymers. Microfluidic channels are also printed on paper to demonstrate the concept of paper diagnostic devices. Liquid- liquid and solid-liquid interactions that involve ink jet printing of biomolecules onto paper are quantified and modelled. This study validates paper as a bioactive support. The ink jet printing is shown as a convenient technique which can be scaled up for diagnostic and industrial applications.