Password protecting digitally signed documents in Adobe Acrobat X Pro

I am looking for the combination of steps to get my digitally signed documents to be password protected for secure distribution. My documents contain new "user password" information and a number of "areas" which require digital signatures to be added.

Any input as to how one would construct a document with :

1. one to three --> digitally signed signatures fields in one document
2. Password "opening" protection for the document containing the fields; both signatures and sensitive data fields
3. suggestions on how to make the document open to accepting more signatures without it demanding the creation of a newly saved document after being digitally signed by one signature

I have worked at this a couple of different ways but am having problems finding the right combination/sequence of steps to make it all come together.

Please assist.....

1. Thanks....