I used to correct international exams, they always sent DHL or some other carrier, FedEx et. Priority to get delivered and intact. I do the same when I send originals. Of course you'll have to charge for it, you should look into insurance (the carrier can provide this).
If anyone complains originals with shipping costs are too much I point them to FAA for a cheaper print option.
A rough calculation: Send 10 regular post, lose one, that one will wipe out my profit for all ten.
Send with a package carrier, insured, sell 8 (price difference), no worries, any loss refunded to me and payment refunded to customer. Overall no net loss.
The only exception I make is small items on postal routes I know to be reliable, neglible loss.