Hi crstr,
Yes, you can directly upgrade.
See the upgrade paths in 8.3R2.1 PCS Release Notes
https://www.pulsesecure.net/download/techpubs/current/981/pulse-connect-secure/pcs/8.3rx/pcs_relnotes_8.3r2.1.pdf
Thanks,
Ray.

Pulse Connect Secure Certified Expert