N.B.: As with any "free" software, there may be restrictions, which are always specified in the software's licensing agreement, typically known as the End-User License Agreement (EULA). I encourage you to read the entire EULA of this product to be certain that you are in license compliance.
This new video Micro Tutorial shows where to download the free Foxit Reader and explains how to use it to place a date-time stamp on a PDF file.
1. Download and Install the Free Version of Foxit Reader
Visit the website for Foxit Reader at Foxit Software: