Of course. Posting articles on your site may even help in your efforts to rank higher within search engines like Google who look for content related to the products you are selling. Quality written content also makes you seem more credible in your niche, especially if the articles teach something or provide information to your users that helps them.
It is extremely important that you do not use articles that have been mass distributed throughout your market or syndicated onto hundreds of other related sites, as it creates content on your site that is duplicate to content on someone elses site. Duplicate content (text content that can be found elsewhere online) is unoriginal, and your potential customers may notice that you have used content similar to other sites they have seen. In addition, having the same content as other sites will make it harder for you to establish yourself as an expert in your niche market.
Search engines also look for duplicate content during their regular crawls. If a search engines happens to find duplicate content or content that is very similar to someone elses, they may not rank your site as high as it could potentially if the duplicate content was more unique to their index. It is very rare to have a search engine penalize you for duplicate content, but it is highly likely that they will filter out pages that appear to be duplicate.
Remember that quality written articles will help to increase your search engine rankings and helps to establish trust in the eyes of your customers, but the content should be unique. Many online merchants use catalogs that are copied straight from the manufacturers descriptions and specifications. Copying product catalogs word for word can often times create a bad user experience (most people read paper catalogs different than they read online catalogs), hinder your ranking efforts and may even provoke a search engine filter. If you use a catalog in this manner be sure to change the product names, description content and text layout so that it appears unique to your store users and search engines.