A document generation system creates a secure document by: receiving document content to be printed onto a substrate; creating a stencil mask comprising an image of at least a portion of the document content; receiving an image of a watermark to be printed on the substrate; modifying the watermark to remove portions of the watermark that will correspond to locations of the stencil mask; causing a print device to print the document content on the substrate; and causing the print device to print the modified watermark through the stencil mask on the substrate.