A PDF file is 100% reliable, right?
For most lawyers, a PDF file (or even a scanned document for that matter) is unassumingly relied on as being tamper proof. Corporate lawyers love to save contract execution copies and standard form agreements as PDF files for these very reason. However most commercial PDF software (e.g. Adobe Acrobat, Nitro) these days have PDF editing capability within document.
For the paranoid lawyer, without the original document its impossible to detect what has changed, although a tell tale sign that a PDF document has been modified is to check for any difference between the document create and document modify time stamp in the PDF document properties. In fact embedded document metadata (PDF or Word) is often overlooked and can provide some useful historical information for a counterparty’s counsel. But, that’s a topic for another day…