I had a similar situation in which the signed form would need to have an addtional page when viewed in Workspace.
Using attachments, I have been able to overcome the problem. I created 2 forms. One was the signed document and the other was the additional page. I use the additional page as xfaForm variable in Workspace and the signed document is the attachment.
This way the user can manipulate the Workspace form and verify the attachment (signed document). This will prevent the signature from breaking.