If you have already fulfilled the order (and it isn't visible in our app anymore) you will need to log in to your MyPost Business account and go to the Transactions page where you can choose the batch of labels to reprint.
Go here to find your labels : https://auspost.com.au/mypost-business/transactions
If the labels haven't been fulfilled in our app yet, you can just click the Actions or Bulk Actions (when selecting multiple orders at once) button for the order in question and choose the Reprint Label option.
To do so in bulk, you can use Print Labels once again, you will not be charged twice.
Please note Australia Post only allow labels to be reprinted for 48 hours after they've been generated.
If the labels are older than 48hrs you would need to print fresh/new labels for your order, and request a Refund for prior labels.