The only time to even consider this question is if you want your website to attract sales or interest from customers who do not know you and are seeking your goods or services over the internet. If your website is just an information service for existing customers then the answer is already a straight forward no, you require no Online Marketing.
If you do want your website to work that way then you need to establish if you need optimization, or if your site is good enough in that region already. The best place to begin your investigations is with your competitors and their listing, compared to you, on the internet search engine results list.
Choose your standard internet search engine, think about your sector and come up with a few quite common words or phrases that describe loosely what products or services you deliver. Then insert these into the search engine one at a time and note down which of your competitors are generally listed on that first page of results. Also scan down each page in turn until you find your own website details ( if this does not happen after the first 10 pages of results you can stop searching!).
At this stage you will be able to gage if your position is a lot lower that the competition or not. If not, and you are listed up there on page 1 of the results then either you have a quite specific product, nearly no competitors or your site is already optimized to the precise level. Do double check at this stage that you have not identified a very specific keyword or phrase for your research as this will twist results dramatically and give you a guarantee good Search Engine Placement!
If you have identified your website way down the listings, or indeed you have not identified your site at all in the first 10 pages then some online promotion in the form of search engine optimization may be worth investing in.
There are professional firms out there who will help you to develop your positioning in the search results and this is important for a decent amount of business. All the firms currently sitting on page one of the search results will draw the attention of at least 85% of the searching customers and as long as that they do actually offer what their potential customer wants they will almost definitely get the business. The customer will certainly not be sifting through page after page of search results when his product is right there on page one.
The SEO Company can make certain that your positioning improves over the period of a month or two and the benefits should then make themselves apparent.