Pressure, strain, and force sensors are critical components in applications such as industrial automation, healthcare, and aerospace. This chapter reviews the operating principles and characteristics of piezoresistive, capacitive, and piezoelectric sensors and analyzes their domain-specific advantages and limitations. We emphasize the dual role of paper-based materials in sensors: serving as structural substrates to provide mechanical support for sensing elements and functioning as active media by harnessing their intrinsic properties (e.g., porosity, surface roughness). Key fabrication techniques such as coating and printed electronics are discussed in conjunction with functional designs aimed at optimizing electrical conductivity, environmental responsiveness, and multimodal sensing. Through novel material-structure synergies, next-generation paper-based sensors are poised to overcome challenges in adaptability, durability, and multifunctionality, thereby enabling integration into wearable electronics, soft robotics, and smart environments.