The Campaign Members of the Campaign for will have the Status updated for the various steps. These are:

• Statement Generated : This is for the first step where a PDF is generated and stored against the Campaign Members related contact record
• Statement Send: This is the status initially assigned when a request is made to send (email) the statement to the Contact. The workflow "Send Annual Statement" is triggered by the Campaign Member Status of "Statement Send" and is the mechanism for emailing the statement.

To manually resend a statement, you could simply change the Campaign Member Status to "Send Annual Statement" and it will send it again.