Watermarks on standard PDFs are essentially text and/or graphics that are included as part of the PDF document itself, i.e. they are editable elements that form part of the page content on one or more pages of a document. They can be placed in a range of positions on the page. In the original 1.7 version of the standard watermarks are described as annotations:
- A watermark annotation (PDF 1.6) shall be used to represent graphics that shall be printed at a fixed size and position on a page, regardless of the dimensions of the printed page. Watermark annotations shall have no pop-up window or other interactive elements.... When displaying a watermark annotation on-screen, conforming readers shall use the dimensions of the media box as the page size so that the scroll and zoom behavior is the same as for other annotations.
Many PDF documents include a copyright statement at the start of the document and/or in running footers. In addition Static and Dynamic Watermarks may be added to provide a level of document security. With Adobe-style "static" watermarks many tools exist for watermark removal, so this kind of watermark only provides additional security if included in a DRM protected encrypted PDF (see further below) where the document cannot be decrypted. Dynamic watermarks are displayed when the document is viewed and use variables to identify things like the username, their device and the date and time. In this case the security provided is strong because the watermark cannot be removed.
Static watermarks are created by using a tool such as Adobe Acrobat or A-PDF to create an additional foreground or background item on some or all pages of a PDF. The screenshot below illustrates this using Adobe Acrobat XI, and as can be seen, the text entered appears on the selected page – here as a simple text string, in the color, size and orientation selected. Adobe Acrobat and A-PDF are very flexible in providing options for statically added watermarks of this type. Once added the PDF must be saved, so that the additional content form a permanent part of the PDF file itself. If this file is then protected, using Adobe’s standard security facilities, preferably with a longish password (8+ alpha-numerics) then the watermarking will have a reasonable level of protection against removal. Note that the watermark can contain any statically defined information you wish, so can be generic, e.g. “(c) My Company, 2019”, or “!This file has been issued to Mr A B Johnson of XYZ Inc – no copying of this file is permitted”. Our DrumlinPublisher software supports personalized static watermarks of this kind within a fully encrypted DRM environment (see further, below)
The second approach is the use of dynamic watermarking. As with static watermarking a dynamic watermark can contain static text, such as “(c) My Company 2019”, but that misses the real value of such facilities. The main feature of a dynamic watermark is that it includes information generated at the moment of display or printing that includes (additional) end user or other information that makes the file “unique” and identifiable.
In the example below there are both static and dynamic watermarks included. The static watermark has been added to the source document using Adobe Acrobat – in this case it has been placed at a diagonal angle across the text in such as way as to extend across the page but with minimal interference with the text. The dynamic watermark, created using DrumlinPublisher, is shown at the foot of the page, and includes information about the file displayed (the filename itself), plus information that identifies the user (via the partially displayed code), the device on which the document is displayed, the date and other information. This information is dynamically generated when the file is displayed and is overlaid onto this viewable screen window rather than embedded in the document. This means that when the page is zoomed in or out, the dynamic watermark is always displayed in front of the viewable area. This provides an added level of protection for the document against screen capture that is now a standard feature of many operating systems and hardware devices (e.g. a built in feature of Android and iOS mobile devices). There are also a range of server-driven tools and PDF security products that will automatically stamp or watermark PDF files that are downloaded.