Previously, this question was not even on the agenda for small or medium business. The cost of typical BPM solution was far bigger than a business could afford. Now it's completely different. The Open Source solutions like Intalio and Bonita allow small/medium businesses to use these technologies not for free (nothing is this world is free, even Free Open Source Software), but for very affordable price of business analytic's services without license fees.
Besides the cost business has a problem with understanding of BPM, which sometimes referenced as workflow. Of course, BPM is a serious term which includes many things like ideology and complicated technologies, but do actually business need to know all that staff to have advantage of using BPM? I think no.
If you have a business and it grows, you'd probably like to know if you need this modern advanced thing called BPM, but you wouldn't like to dive into it like IT Pro. The recipe is pretty simple: look at your business and try to find if you have some written instructions for your daily business activities like invoicing, processing orders, working with warehouse, etc. If the answer is yes, you can definitely benefit from adopting BPM approach/system. Just think about BPM as a special manager who will make sure that everything is going as written by instruction, notify you immediately if not and provide a detailed report of how is your instructions being executed. The other thing you'd like that if you need to slightly change your instructions, you'll just make a few changes on a special diagram using your mouse and that's it. Thus the system will encourage you to make you business processes even better. The BPM will increase productivity, dramatically reduce number of mistakes and increase your understanding of how it is going.
So just let specialists help you.