1. Determine the part of the model you would like to print, turn off all unwanted layers
2. Using the Create Fence or the Clip Volume tool, select the area that you want for the printed model. If using the fence tool, make sure that Clip is selected.
3. Save the section to a new file to be edited. This will prevent the original data from being lost. With the fence tool, this can be done by using the Copy/Move Fence Contents to File tool.