This letter analyses the achievable performance of Low Earth Orbit (LEO) Position-Navigation-Timing (PNT) using the novel Orthogonal Time Frequency Space (OTFS) modulation. While originally designed for communication purposes, we show the advantages this modulation may bring to the PNT domain, in particular for doubly-selective channels exhibiting both delay and Doppler spreads. We show how the LEO channel fits this description due to its fast dynamics, and we present the improvements of using OTFS with respect to the standard Binary Phase Shift Keying (BPSK) modulation in terms of delay-Doppler estimation accuracy, in addition to a comparison of their respective Multipath Error Envelopes.