If you want to sign a document, and you want other signers to add it as well, you'll want to send a signature request using the Me & Others work flow.
After you've uploaded the document that you want to have signed, you'll need to add additional signing roles to the document so that you can list each signers' name and email address, as well as your own. You can add additional signers to the document by clicking the "Add Signer" field below the name and email address fields. You can have up to 20 signers on one document.
Be sure to double-check the email addresses of each signer. If there are any typos in the email addresses, you'll have to edit and resend the document to each signer to be signed again.
Once you've added all your signers, you'll want to prepare the document for signing by adding the necessary fields to the document. You can choose the type of field that you want to create from the toolbar at the top of the editor. Next, click the spot on the document where you want to add the signature. You can drag the field to adjust placement. Next, you'll want to select who will sign the document from the drop down menu. After you've set up the fields for each signer, you can click continue in the upper right corner.
From here, you can add a title and message to your signature request and send it off!