How to add a watermark to many PDFs.

Hi @Federico Galimberti 

Hope you are doing well.

When you apply one or more routine sets of commands to your files, you can save time and keystrokes by using an action—a defined series of commands with specific settings and in a specific order that you apply in a single step. You can apply an action to a single document, to several documents, or an entire collection of documents.

Acrobat provides some predefined actions. You can also create your own actions. You can access and manage the actions by clicking Tools > Action Wizard.

For more information about know-how, please go through the help page https://helpx.adobe.com/acrobat/using/action-wizard-acrobat-pro.html

Regards

Amal