Adobe Acrobat Pro 2023

You can't do it in a single process. It has to be done separately. Also, you must know the password for all the files to be able to remove the security policy, of course.

Hi @Nuno H 

Sorry for the delay in response. 

If you have access/ permission to remove the password protection from files, then you can merge them all b applying an action with the help of Action Wizard. 

Here's a complete guide on how to create or delete an Action https://helpx.adobe.com/acrobat/using/action-wizard-acrobat-pro.html 

Thanks,

Akanchha