This paper investigates an innovative approach to enable Joint Communication and Positioning (JCAP) in 5G Non-Terrestrial Networks (NTN) using Low Earth Orbit (LEO) multi-beam satellite systems. The integration of communication and navigation services is achieved by aggregating a Direct-Sequence Spread Spectrum (DSSS) navigation signal with a 5G Orthogonal Frequency-Division Multiplexing (OFDM) waveform. Two models are proposed for resource allocation and signal aggregation: shared beam model where communication and navigation signals are aggregated before the Beamforming Network (BFN) sharing the same beam; and independent beam model, which has separated beams for communication and for navigation, where the navigation beam is intended to be much wider than the communication beams overlapping these. The models are analyzed using the spectral efficiency for communications and the Cramer Rao Lower Bound (CRLB) for the range estimation used in navigation as optimization objectives. The study formulates and solves a multi-objective optimization problem deriving the Pareto front, and highlighting the trade-off between communication and navigation performance. Extensive simulations demonstrate the efficacy of the proposed models in terms of spectral efficiency and accuracy in range estimation. The models have been tested in two different scenarios, one without frequency re-use between beams and a second scenario with a 3 color frequency reuse. The results show that the independent beams model outperforming shared beams model in navigation accuracy due to reduced beam interference in both scenarios. The proposed solution provides backward compatibility with existing 5G NTN, enabling uninterrupted positioning and communication services in GNSS-denied areas. This work lays the foundation for robust and efficient JCAP implementations, addressing challenges in multi-beam interference and resource optimization.