When proofreading a client’s work your job is not only to rectify the wrong spelling and fix misplaced or missing punctuations. You also have to ease readability by splitting lengthy sentences, and wherever necessary, putting the right words in place of the ill-fitting ones. Then there’s the part when you have to ensure that there are a good flow and coherence to the overall text.
It’s no mystery why such task needs to be handled by someone who has a keen eye for details and who has a patience of a saint. All this points to one simple fact - clients should give proofreaders ample time to do their job well. No normal human can do an urgent job as well as she would have done if given enough time to comb through a document. If time is on a proofreader’s side at least she could painstakingly go over the text slowly and thoroughly. This would help ensure every word, each period or comma, and paragraph had been checked in minute detail. Thus, every little mistake is able to be detected instead of being glossed over due to lack of time.
That is why you won’t be able to do a proper job if you’re being rushed to do it fast. I know some proofreaders burn the midnight oil in order to finish the job on time. But this normally comes at the expense of their health. There had been a case of a proofreader who suffered from eye problems soon after proofing a massive amount of document day after day (and nights too) just to meet deadlines that were alarmingly looming near. There was a good chance that she had underestimated the amount of time needed to do the job. She could have hastily taken the job and agreed to get it delivered by the deadline given by the client.
There is an important lesson here for the clients and proofreaders alike. Clients should not submit their documents too near the deadline and yet expect the proofreader to be able to give her best in performing the task of proofing and editing. Yes, sure some of us can handle it but remember working under tight deadlines for a number of clients at the same time would take a toll on the proofreader. Thus, her work would suffer and she wouldn't able to finish a job as well as if she had been given ample time to do it.
As a parting advice, a proofreader should always know her limit and know when to say no. Sure, taking up more jobs means more income but you owe it to yourself to keep your health and sanity in check at all times.