My first thought would be to import file to iSeries & then query the file. You would have to recreate page breaks.
Another possibility would be to create an AFP printer (IBM 4028) that prints to a file instead of a device. Print the text file using the AFP printer to a shared folder on the iSeries. Create a physical file (CRTPF FILE(LIB/FILNAME) RCDLEN(256) MAXMBRS(xxx) LVLCHK(*NO)). Next copy the doc from from the folder to a physical file (CPYFRMPCD FROMFLR(FOLDERNAME) TOFILE(LIB/FILNAME) FROMDOC(DOCNAME.PRN) TRNTBLE(*NONE) TRNFMT(*TEXT)). Now you have a physical file that you could try to create a spooled file from. Or you could create an overlay from here, I’m not sure what the results would be with a multi-page file CRTOVL OVL(LIB/OVLNAME) FILE(LIB/FILNAME) DATATYPE(*AFPDS).
Not sure if this solves your problem or not but hopefully it will give you a start.