There are lots of ways to hire translators. A good historian ideally will learn the language, though, to avoid the intermediary. Obviously that takes a lot of time. But working only with translations through translators is not something that an an academic historian is likely to do if they are doing a lot of work in another language. In my experience it is very much looked down upon when you find out that someone doesn't know the key language they are working in — there are lots of cases of Anglophones writing about Nazi Germany who don't speak any German, for example, and that's taken as a sign that they are not that serious (especially since German to English is not considered an exceptionally difficult transition — not like, say, English to Chinese or Japanese). "He doesn't even read German," is the kind of dirty thing that professors whisper to one another about others' work.

To get a history PhD in the USA, you generally have to show language proficiency in at least one foreign language (for mine, you needed German and French, but you could substitute one or both with languages more relevant to your research — I did Russian instead of French).

History professors often have students who speak other languages and can use them. I have frequently hired native-speaking undergraduates to help me with this kind of work — not relying on their translations, but their ability to skim texts and documents for things I am interested in exceeds mine, for sure. My student body (STEM, mostly) has lots of native Russian and Chinese speakers, for example.

And there is always the possibility of collaboration with other scholars. When I wrote [an article a few years back](http://alexwellerstein.com/publications/wellerstein_geist_secretssoviethbomb(pt).pdf) that was heavily reliant on Russian sources, I did it with a historian friend who spoke Russian fluently, because my Russian was not quite good enough to do it with high confidence (and I valued his insights as well — he was not merely a "translator" but a real collaborator).

These days there are lots more options for internet-based translation services than there ever were before, but the idea is the same. And of course we have Google Translate today, which is not good enough for real publication use, but can speed up a lot of casual browsing/searching (I will plug entire documents in Russian or German into Google Translate, just to get a gist of what it is saying in seconds, as opposed to the relatively slow process of actually working through the translation manually).