I have two questions related to XI:
1. I can sign documents with a certificate, I can password protect documents to prevent content being copied, however I can't see how to do both?
2. Is there any way to batch sign multiple documents?
to 1. use following steps:
Using the Place signature option under Fill & Sign you may create the signature with certificate, which you may applied to the documents. For that please refer to this KB article :- https://helpx.adobe.com/acrobat/using/certificate-based-signatures.html
For securing PDF's with password please refer to this KB article :- https://helpx.adobe.com/acrobat/using/securing-pdfs-passwords.html
Would like to inform you that its not possible to batch the multiple PDF documents in Acrobat XI, you have to manually sign documents one after one .