Examination of printed documents to determine issues such as their method of production, whether they were produced on a typewriter, ink-jet printer or a laser printer for example.
Examination of documents for any unique printing or photocopied features that might link them to other documents.
Identification of the 'hidden' yellow dot counterfeit-protection code deposited by colour laser printers and copiers in an attempt to link documents together.
Please note - I cannot decipher the yellow dot code to determine the serial number of the printer. This information is only available to high-level government organisations.