PDF files can be protected from unauthorized copying in multiple ways. One of these is by the inclusion of watermarking, which itself comes in many variants.
The first is the pre-loaded static watermark. If watermarks are added statically they are generally created by using a tool such as Adobe Acrobat or Infix to create an additional foreground or background item on some or all pages of a PDF. The screenshot below illustrates this, 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 is 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, 2013”, or “!This file has been issued to Mr A B Johnson of XYZ Inc – no copying of this file is permitted”
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 2013”, 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, which includes 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 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 Drumlin, 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 iPAD mobile devices). There are also a range of server-driven tools and PDF security products (e.g. those from Adobe, Vitrium, Foxit and others) that will automatically stamp or watermark PDF files that are downloaded.