Multiple users sign document ? HOW?

Hello.I have a document, and want that some users(number of them is changing) sign that doc.

I know how to sign doc with single signature(single user), and how to sign doc with more signatures when I know how many sign’s i need, but I dont know that number.

How can I do that ?

Thanks.

Subject: Multiple users sign document ? HOW ?

Can you tell me how to sign a single document.Thank you!