Even though your object(s) are located on the other pages that have been expanded, Claris CAD enlarges the "Drawing Size" based on the "Handles" of object. A problem that you may see is that an arc with it's center will extend to the right or left of the current page. The handles of the Arc that extend off the page will increase the "Drawing Size."
If you have deleted or moved the objects and there are sill empty pages, you can delete them by selecting Drawing... under the Layout menu. There will be a large square on the right of the dialog that shows the current drawing size. Clicking in the upper left hand corner of the square resizes the drawing area so that it only accomodates objects and handles that are actually on the drawing.
There is one anomaly that we are aware of in Claris CAD 2.0 that will still not allow you decrease the drawing size of your document, even if you do not have any Arcs on your drawing.
If you have selected objects that are on different layers and dragged them to a different location on the same page and typed Command-D (for Duplicate) as you were still dragging these objects, you may not be able to resize the drawing size. If you do an undo right after you see this happening you will be able to decrease the drawing size. If you have done any other drawing function in Claris CAD you will not be able to recreate the drawing size of the document.