In business and personal life you occasionally will need to send documents overnight mail or overnight parcel. You can do this via the United States Postal Service but for critical documents being send from places with a regular or easily scheduled FedEx pick up location, I typically send FedEx. Not that I am specifically endorsing FedEx, it is just that my workplace pays for the shipping of documents if they 'go' FedEx and I have written up the FedEx Air Bill (ie Way Bill) a million times.

International shipping delivers a lot of nuances when it comes to rules, regulations and, of course, charges for services. Customs houses, freight forwarders, steamship lines, you name it will all want to get paid for the goods you ship.
One term that you'll eventually come across on your invoice is the Bunker Adjustment Factor or BAF. I wrote a very brief article on the subject and linked it below. Check it out.