Editing PDF's After Signing (Adobe Professional 8)

Hello All,

I have a Request For Change document that contains two sections that needs to be filled out at seperate dates. Is there a process in which a user can fill out the first part of the form, digitally sign the document, continue on with the second part of the form at a later date, then digitally sign it again (there are two different signature fields)?

I am using Adobe Professional/Reader 8.

Thanks,

-Ben