A professional patent draftsman understands the technology behind your invention, your product, and legal nuances of the patenting process. So having a patent attorney or a patent agent to review before filing is a must.
Professional patent draftsmen have in-depth knowledge about the patent drafting best practices. That may save you and your efforts from multiple question-answer sessions from the patent office, which is also known as, Office Action Response”.
Patent services firm can also assist you with the prior-art search. They can search (in-depth) for prior-art(s) including non-patent literature in the same technology area keeping in mind, the claims, which are the most important part of the patent since they define the IP rights conferred by the patent.