PDF Watermark is a free tool that can add text and image watermarks to PDF files. It also supports batch watermarking these files too.
Download and install it from here.
The interface is minimalistic and simple.
Using it involves adding the source PDF file to be watermarked, choosing the type of watermark and finally adding it.
First, add the source file by clicking ADD PDF. Then choose the destination folder where it will be stored as a watermarked copy.
Next, click SETTINGS and choose the type of watermark.
For text watermarks, font size, color and text can be customized. For image watermark, settings include changing opacity, tilling watermark, scale ratio and more for the source image. Also, the selected watermark can either be applied to all the pages or on the first/last ‘n’ number of pages.
Once finalized, hit the START button for the process to begin.
After the watermark is added, confirm if pages are watermarked from the generated PDF copy in destination folder.
Simple, free and easy.