cffunction - Accepting and Returning PDFs in memory

Hello,

This is something that I should probably know by now in my CF career, but up until now I have never thought/had to do this type of thing.

I have defined a couple functions that I would like to handle accepting, manipulating, and returning PDFs in memory. What data types should I be using for accepting and returning the PDF in memory between functions?  I would prefer to stay away from "any" if possible, but let me know if that is the only choice.

...

<cffunction name="AddMeUhWaddaMak" returntype="any" access="public" output="no">
        <cfargument name="src" type="any" required="yes">
        <cfargument name="name" type="string" required="no">

         ...
               <cfpdf action="addWatermark"
                        source="#arguments.src#"
                        name="#arguments.name#"
                         ...>
                     <cfreturn arguments.name>

</cffunction>

...