Enable of combining PDF documents after it was signed via Adobe Sign

Hello to everyone!

We are using a corporate Adobe Sign and experiencing an issue when after sign a document and then trying to combine via Nitro Pro, it requests a permission password. Right after you sign a document, it becomes SECURED and it`s impossible to remove restrictions, because you need to know a permission password for that.
I have read some articles regarding that topic, and it says that the document owner the one who sets a password, but as a document owner I didn`t set one. And as a solution, they offer to "damage" the document through printing, and it works, you can combine the signed document with others, but the validation is breaking too, you can`t go through the hyperlink of the signature and check the validation, it becomes inactive.

If you could help me with this one, it would be much appreciated.
I would like to know how can I find out the permission password which sets right after the document is signed? Or maybe it`s possible to turn off the automatically setting of a password?

As an example, I attached the signed doc.

Thank you a lot for your time!