If you need to make careful, distortion-free measurements, Eschenbach offers Precision Scale Magnifiers that accept interchangeable measuring scales. The Precision Scale Magnifiers are available at 7x and 10x. The 7x is most versitile for document examination. Each unit has a clear plastic base which allows light into the field. An option is to combine the unit with an adaptive head that allows the scale magnifier to be used with any of the illuminated handles.
Several scales are available.
My two favorites are the linear scale and the combination scale. This 7x Precision Scale Magnifier is fitted with a linear scale that is marked in tenths of a millimeter. The combination scale offers several useful measurement options. If you need a good work light, Eschenbach offers an excellent halogen desk lamp. It is small, bright, and sleek.