The document (secondment agreement) was handed in English, but it was evident that the initial document had a Croatian origin. My task was to make a German (Austrian German) translation, which was an extremely hard job to do.
First I made the rough translation, went through it on more occasions and finally gave it to a German proofreader, who has been increasingly dealing with such documents. I wanted to make sure that the translation was precise, as it was to be given to the Austrian Employment Agency (AMS).
When the proofreader finished the job, my last step was to certify the document.
Good resource: http://www.entsendung.at/