If your scans are .PDF files, you may be able to capture them this way:
Using the 'snapshot' tool (version 8 or higher of Acrobat Reader), draw a marquee around the intended object to copy to the clipboard. Then open a new file in an imaging editing program such as PhotoShop. In most cases the new file will be the same size as what's copied to the clipboard (I know it is in PhotoShop), then paste the image into the new file, edit-resize as needed and save as a .JPG.
The snaphot tool captures at 72dpi, so enlarge the original if you want to then reduce size while increasing resolution, i.e: 300% enlargement to get 300 dpi resolution.