I have seen registrars take different directions in pre-assessments. My advice is to approach it from the point of view of document validation. Yes - you’ve gone through a document review. Now is the time to go a bit further and to have the individuals involved actively involved - explaining their systems. But - try to keep things limited to your major systems. At this point there is not much use in having the lowest level employees go through the inquisition. The compliance to the standard issues are important to validate now.
Hopefully you will have been driving your implementation project in part through internal audits. These should have brought home to the ‘masses’ the idea of the audit. You should have already identified whether or not everyone understands their documentation, is completing forms as required, etc., etc.
In short, make sure you come out of the pre-assessment knowing that major required systems are in place, compliant and are implemented and being used. During the assessment audit you can withstand a few minor nonconformances, but 1 major and - well, you might as well have put the audit off because the registrar will be back before they ‘recommend’ you for registration.
Some registrars require a pre-assessment. Some do not.
A pre-assessment is a valuable tool. Your relationship with your registrar is going to be an intimate one. Interpretation of the requirements with respect to your company and ‘the intent’ is a big factor in a registration. During this visit you will ‘get to know’ your registrar.
The man-days for the pre-assessment are typically about 1/3 or less than for the registration audit.
The pre-assessment is, like the registration audit, a sample. Everything will not be looked at.