They are more expensive than machine translation services, and they do take time, but for important documents, you must go with these. That is because a human translator will reason things out and translate and expression correctly where a machine will fail to do so. The Internet has given people the power to do this. It is up to you to make sure that your selected translation service is not only established and reliable, but the translators also understand the languages fluently and the business or product you deal in adequately. Get a copy of their profile to prove this.
Language is dynamic and ever changing.
Remember that languages soon become 'outdated' for those who do not live in the country of their native origin. Ask for a test project, free of charge, and have somebody verify the work. If you do not know a suitable person, you could ask a university in the destination market to check the accuracy of the conversion. This is particularly important because even if the translator knows the background of your industry, your company might have its own company phrases and terminology that you would want to keep consistent worldwide. In the electronic age it is easier, faster, more reliable, and more efficient to move file around electronically.