Nanotechnology has the potential to significantly impact economic development through the use of various materials, devices, and systems at the nanoscale. The focus of this chapter is on the application of nanoparticles in the pulp and paper industry, highlighting various functionalization techniques that can enhance the existing properties of paper products. Nanoparticles, such as silver, zinc oxide, and titanium dioxide, in addition to carbonaceous materials like graphene oxide and carbon nanotubes, can improve the mechanical, barrier, antimicrobial, and smart properties of paper. The chapter covers various approaches for applying nanoparticles to paper products, including techniques such as impregnation, in situ synthesis, and blending with biopolymer matrices, as well as the associated issues of uniform dispersion, recycling, and biodegradability. Despite progress, significant research gaps remain, particularly in understanding the long-term environmental impacts of nanoparticle-functionalized papers and the scale-up of their applications. This work highlights the importance of interdisciplinary research in assessing the safety and effectiveness of such materials in real-world applications, contributing to a broader understanding of how to improve the sustainability and performance of paper products within the context of a circular economy. We have demonstrated the transformative potential of nanotechnology to enable lightweight, multifunctional, and environmentally friendly paper products.