The New York Times > Technology > Circuits > They Are Sleuths Who Weigh Prose "The document forger's job has been made much simpler with the help of image-editing programs like Adobe Photoshop. Documents created in a word-processing program can be cleaned up, blurred, resized, or otherwise manipulated using Photoshop's arsenal of drawing and painting tools, special effects and filters. A forger can electronically copy a signature from an authentic document, tweak it in Photoshop and then paste it into a new document. To the untrained eye, the fake composite is often indistinguishable from the genuine article.
But document examiners have several counterweapons that can help detect sophisticated digital cut-and-paste forgeries. One is a digital image analyzer, a high-resolution digital microscope connected to a computer with image-analysis software that can distinguish and measure microscopic characteristics of the document - everything from the wicking qualities of the ink to pen pressure."