In this research work, electrically conductive paper composites were prepared from polypyrrole-engineered pulp fibres by two methods: (a) exclusively from such engineered fibres; and (b) from a mixture of the modified fibres and unmodified ones. Both composites were investigated for their conductivity and strength properties as a function of monomer dosage or percentage of treated fibres in the mixture. It was found that, for the "mixture" method (i.e., by adding treated fibres as conductive fillers), less monomer (i.e., conductive polymer) was needed to achieve the same conductivity while a higher tensile strength in the paper was attained when comparing with paper obtained exclusively from treated fibres. The percolation model was adopted to describe such paper-conducting polymer composites, and the much lower percolation threshold achieved through the "mixture" method can be explained by a multiple-percolation theory. The. long-term environmental aging stability of these composites was also monitored, and attempts were made to interpret the observed conductivity decay through existing kinetic models.