Yikes! I would never "LEAN" on a scanner. That's a good way to break the glass, cause physical contact with the scan head, or otherwise cause damage to the scanner. I would use no more than moderate pressure on the top of the scanner.
Once in Photoshop, it should be a simple matter to select the shadow area and clone it out of existence. Zoom in so that the shadow area can be seen well. Try the Magic Wand, but remember to adjust its sensitivity so that it does not select areas of the image that you do not want selected. You can select multiple areas by using the Magic Wand in the "+" mode. Another good tool for working with edges is the polygon tool. Select short segments and it will do a good job of following the edge of a document or item. BTW, all of the selection tools can operate in "+", "-", and NEW modes. New means start the selection over again from scratch.