If you are trying to market software products. The absolute best way to go is to offer the for free in exchange of a review.
Find out tech blogs and ask them if they want to start a giveaway for their audience, you will offer a few licenses (+1 for the reviewer).
At the same time offer a discount coupon to include in the review (for those who didn't win the contest), that way you can also get a few sales.
build up a page on your website and offer a time limited giveaway (your product for free for a limited time). I'm sure you have a catalog and different versions. Ex: standar, Pro, Ultimate, etc..
Offer the basic version (with no free upgrades, no support) to the world.
Include an optin form into your giveaway page to capture leads.
If you do it correctly, you could potentially receive hordes of traffic and leads.
this way you get:
1. free backlinks to your site.
2. Free review for your product.
3. overall SEO improvements
4. Potential massive traffic.
You don't need SEO, backlinks or any other forms of paid advertising.
hope this helps