Net Q & A

Question of the Month: July 2002

Is putting material into a PDF file a good way to keep others from changing it?

Answer

Portable Document Format, or PDF, is a proprietary format developed by Adobe, which distributes a free reader that can be used to view files.  An article at LLRX.com, Adobe For Lawyers, does a good job of summarizing how lawyers can benefit from the product.

However, there are dangers in using PDF. Probably because PDF files can't be altered with the word processors most lawyers have on their computers, many lawyers tend to assume that PDF files can't be altered. Even the knowledgeable author of the LLRX article cited above begins his answer to the question "Why should lawyers use PDF files?" by saying, "First, the files aren't alterable and they retain the original formatting."

Unfortunately, this is misleading. Most PDF files can be altered with relatively little effort. The software used to created PDF files, Adobe Acrobat (formerly called Acrobat Exchange), has some editing capability, though text will not reflow if you add or delete too many words. There are plug-ins for Acrobat (including PitStop from Enfocus) that increase its editing ability, and applications like PhotoShop and Illustrator can edit graphics within a PDF file. The Adobe web site explains how to do this. Some other common commercial software like MacroMedia FreeHand and Corel Draw can edit PDF files, and other editors like the Jaws PDF Editor are readily available.

The more recent versions of Adobe Acrobat PDF creation software contain a password protection feature to prevent unauthorized persons from altering files. If this feature has been used, it makes it more difficult to edit a PDF file.  However, for reasons explained in Bruce Schneier, Secrets and Lies Digital Security in a Networked World, if someone can profit by changing an important PDF file, it is probably unwise to place too much faith it it remaining tamper-free.

It is trivially easy to edit most PDF files, and it is probable that nearly any PDF file can be altered by a knowledgeable person who is highly motivated to alter it.

Jerry Lawson