Should the positions description of the employees be reviewed as part of the (Planning, Development and Review) PDR process?

yes it should be . it helps in getting company goals.

Yes from my point of view . as its a cycle well never closed 

as you know PDR process is an opportunity for open discussion between reviewer and reviewee in the following areas: -

1. job performance
2. strengths
3. future potential and career progression
4. setting of objectives
5. developmental needs
6. a review and planning discussion

Thanks

Yes, it should be !

PDR process provides a framework for staff to set performance objectives, review career goals, align to the strategic direction, and prepare development plans that will assist in achieving the objectives. So, the position descriptions play as a key measurement document in this process.

Planning, Development and Review provides a framework for staff to set performance objectives which are meaningful in their current role, contribute to career goals. PDR should also encompass development planning that will assist in achieving these objectives, and allow for a review of performance outcomes between staff and people leaders.

The Performance Development Review (PDR) is not just a set of processes. Used well, it offers a constructive and flexible approach to reviewing your team members in a way that inspires and motivates them to be the best that they can be. It also forms part of a wider, holistic approach to performance management.