Why do I need a professional translator?

Translation demands a rare combination of linguistic and writing skill. Even writers who have become proficient in two or more languages rarely combine these two types of skill well enough to translate quickly and well.

A skilled translator offers benefits that someone who is "only" bilingual cannot provide:

Translation involves the communication of concepts, not just words. The most common mistake an amateur translator makes is to translate each word literally, rather than striving to communicate the author's intended meaning.
Amateur translators often choose words that seem right instead of choosing the ones that are right. The most common such error involves what's called a faux ami (a false friend) in French: words that resemble each other so closely that the translator forgets they differ in meaning between the two languages.
A professional translator will help you identify your most important goal: preserving the author's voice and style and idiom as closely as possible, creating something with a new voice and style and idiom that communicates the same message more effectively in the second language, or finding an acceptable compromise between these two approaches.
Professional translators are subject-matter experts, and have the expert's ability to understand a subject's jargon and communication style. Moreover, we know the right jargon and usage patterns to communicate successfully with different audiences in the target language.
Professional translators are more efficient. In addition to our advanced knowledge of a subject, we use tools such as lexicons and terminology databases to find the right words quickly, and can use a range of tools such as computer-assisted translation to speed up our work and improve consistency. This technology can't yet replace a human translator, but instead helps us complete jobs more quickly and accurately than would otherwise be possible.