add watermark in pdf

Nowadays, office software is used more and more frequently, so we need to know what are the relevant knowledge points about various office software, so that we can effectively improve our work efficiency and enable us to complete our work faster and better. Pdf is one of the com

A long time ago, I didn't know what a pdf was, and it may even be thankful that many students' computers can open this kind of document. More and more later, pdf is used more and more, and slowly, the demand for pdf is also increasing. The most common situation should be that sometimes people need t