Does the "Preparer" automatically carry over from the Pre-Approval

Yes, by default, the "preparer" assigned on the Pre-Approval will automatically carry over as the preparer on the Reimbursement request.

The traveler can change the assigned preparer, or select "Nobody".

Open

See the Travel System Profile articles for information on how to select other people that may prepare travel requests on your behalf. 

The Department admin may also assign preparers for others