There are two obvious options here: destroy previous versions or keep them. Both may be appropriate depending on the circumstances but there are some factors you should consider when making your decision.
Retaining previous or draft versions can occasionally be valid to document the thought process and discussion which led to the formulation of a particular decision or policy.
In this context keeping draft versions of important records such as a new policy document can be very useful both from an audit perspective and also from the ‘lessons learnt’ point of view helping to answer the “why did we do it that way?” type of questions long after people’s memory of the event has faded.
Of course if you do decide to retain draft versions, it is vital that their draft and superseded status is immediately clear. This is where separating ‘draft’ and ‘issue’ copies in two separate folders and the use of ‘watermarks’ as suggested before can be very useful.
You should also, however, consider that the Freedom of Information Act covers all information held by a public authority. It is therefore possible that you may have to release drafts as well as the final version if the request specifically asks for such information.
Where previous versions of a document included particularly contentious views which were subsequently rescinded, or simple errors which were later corrected, this may be something you wish to avoid. Minutes of meetings are a good example of where there is no benefit in retaining misrepresented accounts of the meeting after they have been corrected.
In practice in most circumstances it is usually more appropriate to destroy draft versions once the final version has been approved – after all, if their content had any real value this should have been reflected in the final version.
Doing so helps reduce the overall amount of information being held and removes the risk of people accessing the wrong version by mistake.