As an SME it is virtually impossible for us to hire the services of a good SEO company that is going to spend time optimising the site, adding new content and gaining good links for the site, simply because of the cost involved. Other SMEs are I am sure in a similar position. They would all love to have a web site that ranked highly in google and the other search engines and brought in a constant flow of new business. However to hire an SEO company to do all those things above is often beyond the reach of many small companies especially those just starting out.
However as a company providing services ourselves and 80% of our new business coming via the internet I can thoroughly recommend that you find a company, invest the money because you will soon get the rewards back. If you feel that you still cannot quite afford to go down that path because money in the company is tight then the other course of action I can recommend is to write articles. I kept seeing and reading all this free advice from SEOs out there on the Web about the benefits of writing articles and submitting to article distribution centres and e-zines. I used to think when reading these words of wisdom...