How to merge 2 pdf forms into one print file ?

I have been using Adobe forms for a year or so. Now I have the need to merge together 2 PDF print files into 1 within the same ABAP program before writing the file to my server. To be more exect, I am talking the output coming from structure FPFORMOUTPUT-PDF. Does anyone out there have some input for me on this issue ? Regards, Stuart.