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We trust PDF files too much – and why we shouldn’t

Byron James, Partner with Expatriate Law, explains why, when examining PDFs adduced as evidence, one should not always believe what one sees.

Byron James, Partner, Expatriate Law

Byron James
, Expatriate Law

"But… it is a PDF file…??" was the incredulous response from the bench recently in a trial in which the Court were informed, seemingly for the first time, that a PDF document can be edited. There is a lot of tacit assumption of honesty in family law litigation. We are currently in the process of moving away from hard copies of documents (our office is now entirely paperless, with two exceptions: Counsel who insist on having a bundle printed and the service of applications where permission to serve by email is refused). We are all trying to embrace working electronically. This is of course many years, perhaps a decade, behind a lot of industries, some of whom are now at the point now of deciding that email is far too passé and use WhatsApp for most professional meetings. So much of family law litigation requires the inherent honesty of the participants; we assume a lot. We assume for example that everything we are sent by email in PDF form is from source, unedited, a form of gospel that we rarely challenge. We are in fact often actively discouraged from challenging: how many raised eyebrows would meet a First Appointment Questionnaire that seeks to really go behind the documentary evidence? As opposing Counsel rolls their eyes and rhetorically asks when will proportionately ever become relevant again?

The truth of much of financial remedies litigation is that we rely a great deal on our clients as a barometer. They are usually the first warning system when something is not quite right, they have an idea – even if not a clear picture – of how things should be and are able to give some direction to what is missing. That is not all clients. Some are not able to assist at all; some have partners who have spent a marriage ensuring that they are not able to. Some parties do not have a lawyer to assist them. How many times do we really ask: is this PDF something we can really rely upon? Whereas, provided in a different format (Word for example) our instinct is different: Word is changeable; PDF is fixed.

Much of this comes from how we use software and file types. We are not used to editing PDF documents but are used to editing documents in Word. Third parties, such as banks, also provide their statements and account balances in PDF. If we receive a PDF from a client with a file name that looks like it has been downloaded from a bank, the common assumption is that it is unedited. It takes on a pure form.

The difficulty for practitioners however is if a PDF has been edited, and if that editing leads to a materially different outcome, did said practitioner do enough to safeguard themselves from a claim of negligence? And, ultimately, is it now the duty of the modern practitioner to be alive to these kinds of issue to ensure their clients are best protected?

There is a different difficulty for judges who rely almost entirely on practitioners to be the gatekeepers of such issues; bundles in hard copy do not assist as most of the methods of editing leave no trace in hard copy form; when bundles go fully electronic, judges will still usually receive a copy of the original (i.e. copied into the bundle by solicitors) and therefore no original source with the file to trace. This is made even more difficult when there are litigants in person before a judge. The gatekeeping element has been removed: who has checked the authenticity of the hard copy documents produced at Court? How often does a judge ask during a hearing whether, for example, the bank statements before them, have been edited and do they really reflect reality?

How a PDF may be edited
PDFs can be edited. There are at least five ways in which a PDF can be edited:

1) Adobe Acrobat Pro: This is a software tool you can purchase from Adobe. It offers far more functionality that just the usual Reader DC tool. It enables, amongst other things, for you to be able to edit, manipulate, move and remove text around a PDF file. There is a specific feature entitled 'Edit PDF' on one of the tool tabs. Once in 'editing' mode, the document is subjected to a conversion and text boxes created within the document over the content. The cursor is then able to enter the text boxes and make insertions or removals. The cleverness of this is that the automatic font of such editing replicates both the font and style of the host text, meaning that once an insertion is made, usually it is difficult to see. This goes beyond just copying the font type and size, it literally mimics the previous writing in every way, including if it is a slightly smudged scan and adopts the same spacing. This can lead to a very credible amendment to a PDF that prima facie, in a hard copy bundle, is almost impossible to spot as an amendment. The only way to really spot this is via the electronic file itself (more below).

2) Microsoft Word: It is possible to open some/most PDFs in Word. This simply involves either using the "open with…' function on double click or within Word itself selecting the open file feature and clicking on a PDF file. This will then be converted to Word. This then enables editing within Word as one would normally do with a PDF, and then the document can be saved again as a PDF. Unlike the 'Edit PDF' function of Acrobat Pro this is a much less precise tool. As the whole document is amended into a different format there is far more scope for the spacing, formatting and republication of items to go awry. If one PDF page appears to have formatting issues or inconsistencies, this might be a red flag of a prior Word conversion. It is also difficult to keep page sizes the same on conversion (due to the different ways in which Word and PDFs are read by their software) and so often what is one page of content can be spread over two. The insertion of text into the document does not follow the same clever reproduction pattern as Adobe Pro. It will not mimic every feature, such as font size, spacing nor copy imperfections such as the smudging in words. It only allows the manual amending of words and other content as one would with any Word document, and this makes creating plausible other content difficult within the Word converted PDF.

3) Preview (on a Mac): Preview is the default image viewer on Apple desktop products, such as MacBooks and IMac's. It is included as a tool within most Apple desktop products. Within the 'Tools' feature of Preview is a function entitled 'Annotate' with a sub-folder therein called 'Text'. This will create an onscreen box that can be placed in a position within the PDF where text is to be inserted. Text can then be added into the box. Once completed and in position, 'Signature' can be clicked on and the 'signature', being the text you have inserted, can be inserted into the document. You can also include pictures within the PDF using 'Thumbnail'. The images used can be obtained from anywhere within your computer's IOS. Such picture could include a picture of text or company logo that you wish to insert. Once the image is chosen, it can then be manipulated into position and the size, colour and orientation changed. Whilst the insertion of text via 'Annotate' is a low-level method, the ability to include images (or text, numbers or otherwise) could be more cleverly used to replicate a number or phrase elsewhere from a source into a different PDF to give it the aesthetic veneer of credibility. If done with sufficient skill, and with there being a sufficiently accurate image for the intended purpose to cut and inset, then this will be essentially impossible to spot in hard copy format and only possible by examining the electronic file.

4) Online services: There are certain online packages that allow, through a web browser, for PDFs to be amended. There are clearly wider implications here of sharing potentially confidential information with a third party unless the PDF sought to be edited belongs to the person in question. The process simply involves uploading the document (through usually a paid service) and then using the tools therein to manipulate the document. Some of these sites offer a high level of sophistication within their tools, akin to Adobe Acrobat Pro (in fact most of them simply use a clone of the same base programme, often illegally). Whilst the document itself in hard copy format will be impossible to determine as amended, there are tell-tell signs. Look to the bank statements of the potentially amending party: are there any entries therein for websites with PDF in their name? Are there any PayPal payments between the Notice of Hearing and filing of Form E date that end with ".99" (they always do)? Since they are often sent by email, has, by accident, the client seen an email from such a company on their home computer or otherwise?

5) Adobe Reader DC: This software is commonly used to just view PDF files. Contained within the program is a tool called 'Fill and Sign'. This tool allows the insertion of text into a document via the tab with 'AB…' (and a pen image). It is possible to amend the text size, font and boldness but little else. This is a very limited functionality tool that could be spotted in a hard copy format: is there an item in the document that looks written in a different format from the rest of the content? If there is, do not ignore. It could be the red flag of an amendment.

Has a PDF been edited?
The starting point is to take possession of the 'original' PDF file. If it is sent as part of a bundle, request the specific original file be sent as a discreet PDF. Contained within every PDF file is 'metadata'; this will list the creation date of the file, the author and any dates/times of any modifications. This is contained in File>Properties>Description:


This is a PDF creation of the Word document used to write this article. It contains some of the 'Info Dictionary' which is general information about the PDF file using available information from the IOS at the time of creation:

Be careful however as the Info Dictionary is still capable of amendment after the fact, and so this date is a useful starting point but might not always be definitive. This starting point could well be a default position going forward when receiving bank statements electronically in PDF form with a Form E. A specific request can be made for the file(s) to come with a clear author stamp from said bank demonstrating the authenticity of their creation. This should also be considered an appropriate request in Questionnaire.

There is also a tool within Adobe Pro that can assist you determine what modifications have been made to a PDF called 'Compare Files'. You can access this from 'View>Compare Files' in the top drop-down menu. This file requires you to choose two files to compare against each other. You could therefore choose two files that should be the same (i.e. the 'same' PDF sent twice or sent from different sources) to compare or you can just choose a file at random.

To demonstrate, I have taken the PDF file of this article, made four changes and saved as a different version. The Compare Files tool produces the following [Compare Report]:


The tool shows the following types of change: replacements, insertions and deletions. They are colour coded (replaced: yellow; inserted: blue; deleted: red). The report itself states how many changes have been made to the document, highlights them following the colour coding and even provides the specifics of the change.

The parties to litigation are becoming ever more sophisticated as their access to technology and information online enables them to challenge the fundamental assumptions we make as practitioners every day. The role of the practitioner in this is to ensure that they are satisfied that documents received are authentic and any red flags, as identified above, are raised and resolved. Judges too need to ensure that they their level of understanding is comparable to those appearing before them and that, especially when they are litigants in person, judges are able to ask the right questions and obtain the correct information to resolve any potential issues.