You cannot use the LiveCycle Policy Server API to attach a policy to a PDF document. However, you can programmatically apply a policy to a document by using the LiveCycle Document Security APIs. For information, see the Adobe LiveCycle Document Security Developers Guide.
But how can I get document security developers guide
Right now I m not able to get 'Document Security API'
nor 'Adobe LiveCycle Document Security Developers Guide'
I don't think it is exposed with policy server but i think it will be present with Document Security Server
You cannot apply a policy to a PDF with Policy Server (APS). To do this you require either Acrobat Pro or Document Security Server (ADSS). There is a method in the ADSS API called applyPolicy() that you use to do this. ADSS then uses the parameters to retrieve the policy from (APS) and encrypt the document.