The earliest use of a watermark was around the year 1800. Watermarking was used to ensure the originality of the document. It typically consisted of an image, an emblem, or just plain text that appeared in various shades of lightness/darkness. It was sometimes created manually when the paper was manufactured by introducing variations in thickness or causing density variations in the paper. Watermarks are even used on postage stamps, currency or government documents. Some are clearly visible to the naked eye, while others require careful perusal. The presence of a watermark is an indication of its authenticity. Though not foolproof, it is the first test for authenticity that a document can be subject to, when verifying prior versions.
In the digital era, the demand for watermarking continues, supported to some extent by word processing software. Standard text watermarks, like "Confidential" or "Draft" or an image can be added to a document easily.
The usage of digital watermarking has evolved to a point where it can be added to any electronic file to protect its contents. The presence of a watermark in a document can help clearly identify the version of the document being used. Watermarks also help in content identification, copyright control, copy protection and viewer tracking.
In the context of document management systems in industries like manufacturing or life sciences, document control and ownership can be critical. Effective Document Control is closely linked to the success of the business and its processes. In such cases, watermarking ensures that the author can easily be identified. The modification of the watermark, as a document passes through various stages of distribution, ensures proper tracking as each authorized person is expected to add their watermark after they have edited or authored a document.
Printed watermarks can be added to documents being shown on a screen or being printed out. These document watermarks can be static or dynamic and can prevent copying or be copy revealing. Typically a combination of these is used. The watermarks are typically arranged in such a way, that any attempt to remove them is clearly evident.
Static watermarks do not change, irrespective of the user processing the document either for editing or printing. Just like on a banknote, no matter who gets it, the watermark is the same. Static watermarks are used to prove the authenticity of a document, or make it difficult to produce another of the same document and prove its authenticity. They can also be used to identify the owner. Static watermarks are sometimes used in such a way, that they may initially appear "hidden", but when an attempt is made to make a copy, the hidden watermark is revealed and makes it obvious that the copied document is not an original.
Dynamic Watermarks, as the name suggests, change based on the use of the document. For example in a regular PDF document, it is possible to add a particular watermark when the document is viewed and another one when it is printed. This increases the security. These watermarks will clearly identify the individual / enterprise that are authorized to use the protected document. Dynamic watermarks can also be used as a means of copy-resisting. In this scenario, when a user tries to copy a document, that user's information is also tagged to the document in the form of a watermark. This helps in identifying the original person who tried to copy it. In a parallel scenario, the user information that is tagged to a document in the form of a watermark, also helps identify if the document is an original.
Graphic watermarks can help with creating printed copies that resist document scanning. The printed copy is of an acceptable quality to the eye, but when scanned, it will cause Optical Character Recognition (OCR) software to fail to convert to text correctly, leading to a poor quality of documents being created.
Dynamic text watermarks can be added to a document to identify the name/email address of the person authorized to use/print the protected document, so that their identity is linked to the document more than once.
The appearance of a watermark can be clearly configured to indicate the stage of document creation. After passing through various stages of development and review, a document is normally ready for consumption by a predetermined audience. The watermark on the document can be representative of where the document is in this process. When a document leaves a document control system, the watermarks ensure that the information about the document travels with it.