Exporters need to have either an export licence on their own or rely on a trading, which would carry out the export process for them. There are forwarders who can arrange the preferred means of transportation, and carry out part of the clearance process. Only (but not all) companies who can issue VAT invoices are entitled for exporting directly. Small companies would inevitably rely on trading companies.
Many documents are required, as invoice, packing list, customs bill, and some forms you fill at the relevant bureaus. It's quite a bureaucratic process, as the transactions must be recorded at the Foreign Trade Office, at the Foreign Exchange Office, at the Customs House…etc…
International money transactions are controlled by some governmental organs, so all the payments must be traceable and approved by the relevant authorities.
Export implies also a VAT refund in a variable percentage over the standard VAT rate.