How I put different Images of Stamps in Documents.

Hello, I work for the Dominican Republic Government, and I have a very difficult task to accomplish.

In my agency, employees write different types of documents, in Microsoft word, and they converted to pdf and send it, to be printed and stamped, then scan with all the stamp and send by email to the final user. 

I have been requested on the posibilities of automating this.  The word documents have place and type of stams that the document required, documents may need one or multiple stamps, in different possitions.

What we need to create is take the word document, converted to PDF, locate the location where they need the stamps, and type of stamps.  Digitally add the image of the Stamp, and send the document to the final destinantion by email, not leaving the digital format?

What libraries do I need?  I believe this is possible,  Marking the locations of the Stamps and witch stamp will be mandatory in each document.  What will be the easyest way to do this?  Anyone?  Any Suggestions?

Thanks in Advance,

Pablo.