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It really depends on what sort of document it is. If it is an old document written in pen and ink the paper and the ink can be chemically analyzed to see if they are indeed old. But this is in the case of a forgery. A "simple" reprint will show raster dots that you should be able to see with your Jewelers glasses. I found this image on Wikimedia commons: https://commons.wikimedia.org/wiki/File:CMYK_under_a_microscope.jpg that shows what to expect. Do you have a particular document in mind?