For those at at teaching or comprehensive universities the luxury of having pre-publication access to a professional editor provided by one's university or department is often out of reach.
Options may include:
Professional services are available for hire and an internet search in your subject may provide contact information for many at a wide range of price-points.
Focus on spelling, grammar, punctuation, word usage, wrong words, perhaps some light rephrasing.
Attention to consistency across the manuscript of specific terms, abbreviations or publication formatting style (heading levels, etc); provide some attention to tone or style; make suggestions related to organization, concision or structure in order to enhance the efficacy of the argument; may suggest some conventions of language usage as appropriate for the genre or intended audience; may raise concerns about obvious legal concerns.
Specialists with higher degrees in your research or academic discipline review not only for issues of copyediting as above, but may also: