Magnetic materials have been used in documents for years. Most black and white copiers use magnetic toners to print, even ink jet technology is now capable of printing using magnetic ink. Today the ubiquitous distribution of high technology scanning and printing equipment enables the “casual” user to alter or make counterfeits of high value documents. The forensic community has traditionally relied on the examination of visible features in documents to identify the printing device and also to verify the document's authenticity. Magnetic technology can add hidden information to documents such as stock certificates, checks, airline tickets,identification cards or transit documents. A solution to forensics is magnetic imaging that can convert optically invisible magnetic patterns into an image, which can be then compared with an optical scan. Depending on the design of a security feature, if the magnetic image is identical to a visible picture, a document could be a counterfeit. We will address the issues related to the magnetic scanning of high value documents printed using different techniques. We will also show how magnetic imaging can provide valuable information in understanding alterations to high value documents.