You get only one chance to make a first impression with your writing, be that a dissertation, an article, or a book.
While mastering your word-processor’s editing and formatting tools can help you to present your work more professionally, a key component of the professional presentation you must strive towards is to avoid letting sloppiness slide. Even the most careful readers and writers will find they miss some of their mistakes. That’s where another pair of eyes can be helpful, vital even, because editing your own work is difficult and time-consuming.
You know your writing, your topic, and your thought process better than anyone else. It’s natural for your mind to fill in missing words, to skim over misspellings or sloppy punctuation, and to make connections between points that aren’t sufficiently explained in the text. An outside reader, however, won’t be in a position to overlook those errors. A good reader—like a writing coach—will not only catch those run-of-the-mill mistakes, but will help you to see where your argument is weak or unsupported by the evidence, where you lose your narrative momentum and start meandering, and when you need to rethink your organizational scheme to present your ideas more intuitively. A good outside reader will notice not only mistakes you might miss, but will also notice the connections that are implicit in your text, but that you haven’t yet untangled.
An extra pair of eyes can not only prevent your writing going out into the world with mistakes but also can help you strengthen your work in ways that you wouldn’t realize on your own.