As with language editing, before the editing commences you should specify what editing style you prefer. Whilst all the revisions will be done in a ‘track change’ mode, for you to accept or reject them, and you may expect the editor to insert comments and questions for you when further clarifications are required, you should state whether you are interested in ‘light’ or ‘heavy’ editing. During ‘light’ editing, the majority of required changes to the text will be signalled as comments (e.g., a comment: ‘This sentence does not really support the logic flow in this paragraph, please consider transferring to the preceding paragraph or expanding as a separate section’), with no major stylistic revisions. In contrast, after ‘heavy’ editing, all the required changes would have been made by the expert (e.g., moving the text to enhance logic flow).
Regardless of the editing style, you may ask the expert to justify any changes that they make to the text, as comments. You should remember that, ultimately, this is your text and you, as the author, will decide which comments and edits to accept or reject.