From a user:
I am trying to make hi MB renderings from sketchup (for large posters). Pls advise if this is possible with this software, if if so, how ?
When you render the final image for printing, just set the Render image size to Custom and set the pixel size to be the resolution that you want.
Uncheck Use SketchUp aspect ratio so that you can set the sizes independently.
Here are some poster sizes, from http://www.staples.com/sbd/content/copyandprint/posters.html:
At 100 DPI (dots per inch), an 18 x 24" image would need to be 1800 x 2400.
At 150 DPI, an 18 x 24" image would need to be 2400 x 3600.
Here is a web site that discusses what DPI you might want to use for your calculation:
Keep in mind, the larger the output resolution is, the longer it will take to render.