Google is a awesome traffic source to your website and could be good for your Knowledge Base too. Helpjuice has a nice code and by default is already Google Friendly.
But there a few things that you can do to improve your SEO.
Human readable URLs
When you're adding a new category or question, Helpjuice allows you to edit the slug. You can turn your URL easy to understand by removing the step words or unnecessary stuff.
I.e.: Our article about custom URLs is "Using Custom URLS with Questions and Categories", but the URL is only:
We keep only the important keywords. This best describes what you'll find inside the article.
Use images description
Google reads your content to understand what it is. However, it can't read images, so you need to describe what is in them. For this, use the alt feature of the images as shown below:
By default, Helpjuice templates already has meta tags. However, if you are using a custom theme that is not include meta tags, you can simply copy and paste the code below into your KB.
This are small things but can bring great results to your Knowledge base if done with consistency.