Terahertz radiation is used to sense multiple parameters in paper and cardboard sheets. The work advances from previous results by (i) using a stratified dispersive model approach to (ii) accurately determine caliper (sheet thickness), fiber orientation, and moisture while (iii) evaluating the impact of the spatial inhomogeneity of the sample sheets. A multitude of paper samples with varying thickness was analyzed using spatially resolved terahertz measurements in combination with a highly accurate material characterization approach. The spatial inhomogeneity of the caliper across the paper samples was found to play a significant role, which cannot be resolved by mechanical reference methods. The feasibility to detect low concentrations of moisture, e.g., through absorption of atmospheric humidity, is also demonstrated.