I'm new to using DraftSight, , and I'm trying to understand how to properly use PDF underlays. I'm able to import the PDF just fine and interact with it, but for some reason I can't use a click and drag selection box to select multiple objects that I draw on top of the underlay. When I try to do so it will just select the underlay without creating the selection box, as though it expects that I want to move the underlay around. I've tried locking the layer it's on, but I still wasn't able to use a drag selection box. Thoughts?