SEO question: How do I do SEO for a small commercial website? Adding more pages will make it look more unprofessional, and so not something I really want to do?

SEO Answer: Sometimes small sites can be easier to do SEO for than big sites.

Faults of big commercial sites:
Some big sites that are product catalogs may require significant link popularity to get indexed. Also if you are dealing with thousands and thousands and thousands of pages it can be hard to make them unique enough to stay indexed as search algorithms continue to advance. Search engines are getting better at comparing pages and sites. If the only difference across most pages of your many thousand page site are a few part numbers then many pages may be considered duplicate content.

Benefits of a small site:
If a site is small that makes it easy to concentrate your internal link popularity on the most important issues, ideas, and keywords. Small hyper targeted sites also work well at being able to dominate those niche markets. You can create a site name based on the vertical and use the domain name to your advantage.

If you are trying to tackle insurance then a small site is not going to get you anywhere unless you are targeting niche types of insurance.

I tend to be a bit verbose (which is perhaps why I wrote an ebook ;) but I also do not buy that adding pages to a commercial site makes a site less professional. Web pages are just a bunch of bits, but those bits are your salesmen.

Which site would YOU trust more:

1. Get the lead or sale or the prospective client can screw off. If they want anything they must pay first.

2. Offers substantial information about the products they sell. Also builds credibility with FAQ section, answering common questions along the buying cycle with content focused on the issues that people tend to think are important before making a purchase.

If you hype it enough, have a high price point and get affiliates pushing it hard enough #1 may win, but in most markets most of the time site #2 will win.

If their site is exceptionally small then adding a few pages with about us and frequently asked questions should allow you to build credibility and target new traffic streams.

If competing sites have a huge brand that you can't afford to compete with one of the best ways to chip away at them is to create useful content, tools, and ideas that solve market problems that have not yet been solved.

If your content is great then it may garner some natural citations, but you need to build at least a few links for search engines to trust your site enough to where others will find it.

Some webmasters are also afraid to link out to relevant resources. I think that most good websites link out to at least a few decent resources. Don't be afraid to link at relevant .gov or .edu pages, industry trade organizations, local chamber of commerce sites and other sites that make sense to reference.