Users use PDF watemaark tool because they want to make their PDF file more presentable the most famous app called OSTtoPSTAPP PDF Watermark Tool is the best app for adding watermark. A watermark identifies the owner of the document and includes important information such as contact numbers and website links. It is simple and easy-to-use this program. Users can easily change the position or opacity of the watermark. A logo, symbol, or piece of text is used as a watermark on printed or digital documents. Users can also create a unique watermark effect. You should be able to identify your PDF file if you have a watermark on it. Watermarks can be created using PNG, JPG, and TIFF images only. Install the free demo before using it.