Hi Robert,
Sure. You can do that with the free version. Well, to an extent. If you look in the Styles window you'll find a drop down menu. There are some sketchy styles included. Choose the appropriate library and click on the thumbnail for the style. There are some modifications available under the Edit tab and some other ways to impact how the style looks. You can get some free styles
here. Some of them are ones I've made. There are more styles available
here at a low cost.
The style I used for the desk is one I made. To make your own sketchy line styles, you need to use Style Builder which is included in the SketchUp Pro package.