Brother DSmobile 600 scanner with Apple Image Capture

I am using a Brother DSmobile 600 scanner with Apple Image Capture on my iMac with OS 10.6.8 (Snow Leopard). I want to scan multiple pages to a single PDF but, whether or not I have the "Create single document" box checked, the individual pages always go to separate documents. It's as if the check box is not connected to anything. My wife has same scanner on MacBook Pro and the check box works correctly with her identical scanner. Am I missing something?