You can click on the link below to learn more about sequential signing when sending a Sign Request though you won’t be able to do that with a Sign Request in DocHub if you need 1,000 signers. Even with DocHub Pro, our Sign Request workflow has a limit of up to 20 signers per document (see our pricing page for more details about the limits), so you would need to choose a different way of getting everyone to sign the same document which you may want to make the document Public and invite people to the URL for it and ask them to fill a copy and add their signature. I’ve included another article below for how to do that.
How do I send my PDF as a Sign Request?
How do I publish a PDF form to a webpage for anyone to sign and complete?