The OSTtoPSTAPP PDF Watermark Tool is software that enables you to add a watermark to your PDF files. Watermarks are usually used to protect documents from unauthorized copying or distribution, to indicate a document's status, or to brand documents with a company logo or name. Additionally, it allows users to add antic watermark effects. A watermark identifies the owner of the documents or important information including your contact details and website address. Its primary role is to prevent copying of your documents. We can add a watermark on all PDF pages at the same time. When you apply a watermark to your PDF file, it is much easier to recognize your PDF files. Only PNG, JPG, and TIFF pictures can be used to make watermarks. Users are free to use this software. A free trial period is provided to users.