Secure PDF Watermarking: Add non-removable dynamic PDF watermarks

What is a watermarked PDF?

A watermarked PDF is a PDF document that has a text and/or image watermark added to it which is displayed when the document is viewed and/or printed.

Text watermarks may be static (always remain the same) for example “This document is the property of ABC Corp.”, or dynamic (changes depending on who opens the document, the date/time and device) for example “This document was viewed by Joe Bloggs joebloggs@acme.com on 04/08/2021”.

Watermarks are added as a layer to the PDF document (which is why they are easy to add) and can be made to appear on top of or behind existing document content.

PDF watermarking may use many of the subtleties of the physical world.  If you think of a banknote, some watermarks seem inside the paper whilst others are on top.  You can get something similar with PDF watermarks.

Think of the information being printed as if it were in layers, rather like a sandwich.  The content sits in the middle, and the PDF watermarking can be over, or under the content, or both.  Also the PDF watermark can be set to be lighter or darker than the content.  In this way PDF watermarking is able to ‘blend’ with the content so that it has a more seamless presentation.  This can help the PDF watermark to be less visually distracting – unless, of course, you want it to be very much in your face.

So applying PDF watermarking takes a certain amount of discipline and artistic judgement, it is not necessarily a mechanical process of having a ‘bog standard’ graphic and/or text and applying it to every document that goes out.

What is the point of watermarked PDF files – why add watermarks to a PDF?

One way to improve the security of your PDF documents is to add a watermark to them – see also Using Document Watermarks as a copying deterrent.

PDF watermarks can be used in several ways:

1. to resist falsification
2. as a copying deterrent
3. to display classification
4. to specify the document is not an original
5. to link the document with a specific authorised user
6. to establish who the owner is

Using watermarks to resist falsification

When using watermarks to resist falsification, PDF watermarking is used in exactly the same way as watermarks on banknotes or cheques.  If you try to make a fake it can be made very difficult to exactly copy the PDF watermark, so anyone seeing the document will also see that it is a fake.  This use of PDF watermarking can be very important where official documents have to be printed/printable and must be demonstrated to be authentic.  (This is how you know a 20 dollar bill or a ten pound note are genuine.  It doesn’t mean documents can’t be faked.  There are still fake banknotes doing the rounds and one pound coin in 36 is a fake.  But PDF watermarking is significantly better than doing nothing.)

Using watermarks as a copying deterrent

This might include text such as ‘It is illegal to copy content from this document’, and/or by using dynamic watermarks to display user information so that users are discouraged from giving copies to others.

Using watermarks to display classification

This is the method of classifying documents by adding a watermark to them that displays how the document should be treated.  For example, adding a confidential watermark or a ‘top secret’ watermark as a stamp or text.

Using watermarks to identify the document as an original or copy

This is achieved by adding a stamp or text to a PDF document to mark it appropriately.  For example you might watermark a PDF with “copy” before printing and/or when it is viewed.

Using watermarks to link a user to a document

PDF watermarking is a useful way to link an identity to a document.  The PDF watermark may be something as simple as a unique number which is associated with the authorized user of a document, or it may be their name, email address, company name and so on.  The point of this PDF watermark is to make it clear who the source of the document is if it is not intended to be copied and passed around.  This technique has been in use for a long time to identify the source of documents ‘leaked’ to the press or who it was obtained from by IPR pirates.  The PDF watermark works because the source of the information (whether a leaked or pirated document) usually does not want to be linked to it.  This does mean that when using PDF watermarking in this way you need to have a clear link between the identity on the document and the identity of the entity that it was authorized to.

Using watermarks to establish ownership

The owner of the document may be different to the document Publisher.  If for example a reseller has been given permission to sell a book, report, etc. then they might want to add a PDF watermark that establishes them as the authorized reseller.

PDF print watermarks – add watermark to PDF only when printing

The most common reason why people want to add PDF watermarks only when the PDF file is printed (i.e. no watermark is displayed when the document is viewed) is to prevent printed copies from being easily re-distributed.

The best way to discourage this is for the watermark to display user identifiable information (such as the user’s name, email, etc.).  This can easily be achieved by using dynamic watermarks where user information is automatically inserted when the PDF document is printed.

Locklizard supports dynamic watermarks and enables you to apply a PDF watermark only when printed, only when viewed, or both.

Watermarks for confidential documents: why add a confidential watermark to a PDF?

Many companies need to distribute confidential PDF documents to selected users or third parties but do not wish them to be distributed any further.  As a security measure (and sometimes for classification) they add a confidential watermark to PDF documents (the same as a confidential watermark stamp on paper documents) on the basis that they will be honored.

However, in reality adding a confidential watermark to a PDF document provides zero protection since it is meaningless.  It does not stop PDF files being shared with others.  The confidential watermark can also be easily removed in any PDF editor.

If you want PDF documents to remain confidential then adding a confidential watermark will have no benefit unless you have other PDF security measures in place to make the watermark protected in the PDF and prevent document sharing.

Confidential image watermarks

Locklizard provide our Publisher customers with a range of confidential image watermarks which they can use to add a confidential watermark to PDF documents.  Confidential watermark examples are below:

Does adding a watermark to a PDF make it more secure?

No.  If you use Adobe Acrobat or a similar PDF editor to add a watermark to a PDF document then that does not make it any more secure.

The reason for this is because users can easily remove the watermark even if the file is password protected.  See Removing PDF watermarks.

This is true of all password protected PDF files that have a watermark applied to them and includes secure data room systems that enable users to download watermarked PDF files such as Digify and DocSend.

If you want to add a watermark that cannot be removed then you need to use PDF DRM software that adds watermarks to PDF documents that cannot be removed using PDF editing software.