PVC to bottom of exterior door jamb
I have done this repair many times. I buy a 8 foot length of composite exterior jamb stock for the repair. Not cheap, I think the last one was $33. I cut off the bottom of the jamb with my oscillating saw. On the hinge side I usually cut right below the bottom hinge (about 8.5 inches). You will have to break the bottom free from the threshold, it is screwed or stapled in place. Make sure the jamb is well shimmed behind the lowe hinge. Cut a piece of the jamb stock to length, put in place, shim and secure with finish nails (I use my 16 ga pneumatic nailer). Cut the latch side out and repeat. I also remove the wood brick molding (the whole length) and replace with PVC brick mold. It is important to make sure the jamb is secured to the framing before you remove the brick mold. Often the door is installed by just nailing thru the brick mold. Poor practice but I see it all the time.
Since the threshold will be unattached from the jamb, it needs to be secured down. I drive a few rustproof screws into the sub-floor (or use Tapcons if a concrete slab).
Coastal South Carolina