You can add watermark to PDF with iSkysoft PDF Editor to protect your intellectual and artistic property., you can refer to the following guide.

iSkysoft PDF Editor 6 Professional enables you to add your own watermark to a PDF for protecting your intellectual and artistic property. Open Edit tab and click on "Watermark" button. Select the option "New Watermark".

Then you will get the Add Watermark dialog box. In this dialog box you can enter the text content as watermark that you need and change position of the watermark on PDF. For further settings click on "Advanced Settings" and here you can set the place, appearance, location and page range of the watermark. After that, you can click on "OK" to add the watermark to your PDF. Besides, you can save the settings in Add Watermark dialog box in order to set it as a ready-to-use watermark for adding watermark in batch.

The button "Update Watermark" allows you to change the settings of existing watermark. By using button "Remove Watermark" you can remove an existing watermark from PDF.