Sign PDF in a folder without opening Acrobat

Hi,

Our customer needs to sign multiple PDF located in a folder. I see that it seems possible using Acrobat Pro in batch mode but I was wondering if it would be possible to achieve that task without directly opening Acrobat (calling it from the command line maybe ?).

The customer is producing hundreds of thousands of PDF per month and can't open each one individually. We would like to automate this task so no human intervention is needed.