How to Merge Inter-active pdfs ?

Hi Experts,

I have one requirement is like.....

In my form user can add n-number of attachments after that when he clicks on submit button..all attched documents shd merge (append) to base document.

I can do this if my base doc is non-interactive pdf ...but in my case base document and attached documents(attached docs may or may not interactive) are interactive pdf files. How to handle this in ES3 version? Any ideas or samples....it is very urgent.

Regards,

Srujan