I don't own M92 but just as an idea, maybe you could convert djvu to pdf e.g. using free djview app
http://djvu.sourceforge.net/djview4.html
and then merge those scribbles with pdf (on M92 or PC) or someone could wrote a code for M92 or future M96 to do that automatically.
As for supporting program for .sketch files, maybe this will be of some help
https://www.mobileread.com/forums/sho...&postcount=154