There is described a method for controlling the orientation and/or position of sheets (1) processed on a printing machine, each sheet being provided with at least one marking (12; 15) embedded in the sheet, which marking is embedded in the sheet during manufacturing thereof, prior to processing of the sheet on a printing machine. The marking (12; 15) is disposed in a selected location of the sheet and defines a unique orientation and/or position of the sheet. The method comprises the steps of: —checking for the presence or absence of the marking at the selected location on the sheet and/or of characteristic features of the said marking; and —issuing a warning signal if the marking is not detected at the selected location or if the characteristic features of the marking are not detected at the said selected location. The invention advantageously makes use of features already embedded in the sheets (such as metallic and/or magnetic strips or threads, watermarks, etc.) as control markings for controlling the orientation and/or position of the sheets.