I will explain about PgMP audit process in this post.
Once your PgMP application has been accepted by PMI, you are supposed to make the payment. Upon submission of payment, your application may be selected for audit. PMI randomly selects few applications for audit. You will get mail from PMI about the details of next steps which can be that your application has been selected for audit. If not, you will move to next stage which is panel review of answers of experience summary questions.
In case, your application has been selected for audit, you need to submit copies of highest educational certificate and signature from your supervisor on the programs mentioned in the application. PMI will send you a detailed mail on what are they looking for as evidence and you need to provide the same.
Once you submit all docs/evidences, PMI will take around 5 days to verify and complete this process.