In the present study, novel mixed additives of Chitosan or Paraloid B-72 combined with nanoparticles (NPs) of Ag, ZnO, or cellulose (NCL) were examined for their effects on the mechanical, optical, and fungal inhibition properties of the papersheets produced. The highest tensile, tear, and burst indices of the papersheets were observed for flax pulp treated with additives of Paraloid B-72 + ZnO NP (1%), Chitosan + ZnO NP (3%), and Chitosan + NCL (3%) at levels of 59.93 N·m/g, 18.45 mN·m2/g, and 6.47 kPa·m2/g, respectively. Chitosan + ZnO NP (1%) added to flax pulp showed the highest fungal mycelial inhibition (FMI) (1.85%) against Aspergillus flavus. Chitosan + Ag NP (1%) exhibited the highest FMI percentage (11.48%) when added to pulp against A. terreus. Pulp treated with Paraloid B-72 + Ag NP (1%) exhibited the highest activity against Stemphylium solani with an FMI value of 3.7%. The results indicate that the technological properties of the papersheets were enhanced with the addition of novel mixtures to the pulp.