Editing is necessary when you write in a foreign language, both for a translation and for an original piece.
In the case of a translation, the editing process allows to check whether the source and target texts perfectly match, that is to say whether the original text and your translation match.
Rates depend on how much editing is needed. It can be thorough proofreading in order to fix typos and spelling mistakes, or an in-depth work to ensure natural and idiomatic expression without stylistic or syntax-related mistakes.
I offer to review and correct your documents based on your needs.