I am a freelance proofreader and copy-editor, based in Lagos, Nigeria with over 14 years' experience of working with English language. I am constantly amazed at the number of errors I see in articles, journals, books... - in fact I rarely read one without finding errors present. Areas of weakness include poor grammar, spelling mistakes, lack of style consistency and typos. A great deal of effort goes into writing and I always feel it is a great shame if it is let down by simple typing or grammatical mistakes. I firmly believe that, to sell yourself as a quality organisation, you need to present yourself as professionally as possible. That's where I come in!
Writing, in general, is not cheap and for a small additional charge, clients could be assured of a totally accurate and presentable work. Before going publication, works could be thoroughly checked by me, thus ensuring that the final offering to your client is accurate. My suggestion would be that you consider offering the proofreading service as an optional extra to your clients, rather than build it into your existing pricing structure - this allows for clients who may have their own in-house proofreaders and would not, therefore, have to pay for a service they did not require.
Thank you for your time.
Regards
Izuchukwu