If you want to use unicode spooled file as input for InterForm400 the easiest way is simply to define a unicode AFPDS spooled file. You can do that in these steps:
1.Install a Unicode True Type Font (TTF) e.g. Arial unicode into the IFS, so that AFPDS can 'see' it. This is done by copying it into the IFS within: /qibm/UserData/OS400/Fonts/TTFonts
2.Make sure that the AFPDS printer file is referring to the name of the installed True Type Font name exactly as written inside the font e.g. as below, where the field, FLD1 is written:
A FLD1 2G 10 5FONTNAME('Arial Unicode MS Regular+
A ' (*POINTSIZE 15.1)) +
A CCSID(13488 *NOCONVERT)