Dear Michael
DOC and RTF are Microsoft formats. I am not "100%" sure about your requirement.
a.) a WWI document is a "word" document
b.) as you know;: you can "convert" the WWI documents in report distribution to "PDF" file
c.) In principle: using the WwI.Ini file together with the Word functionality you canthink about to write a "macro". But I am 100% about you business demand (there is an "Exit" in the WWI.Ini)
a.) you can handle: pdf, Doc etc. as "Inbound" documents (with assigned application); these documents are in "released "status then. E.g. you could then use CG54/CG50. And if you "display" the document the local WWI is called (and then by some clever architecture you can convert the file from x to Y Format
The WWI_COMPRESS etc. functions are one example of "clever" use of SAP together with an "add on" program: I never tried it: but as you have always a "word" integration in SAP you could try to generate a "DOC => RTF" Function module or a "RTF => DOC" one. and then you could try to use a kind of "similar" architectures as with the "compress" approach
Check may be:
Convert OTF to DOC - Toolbox for IT Groups
So there are some options in SAP.
C.B.
PS: check: CONVERT_ITF_TO_RTF Text Conversion ITF (SAPscript Format) to RTF - Function - ABAP - SAP