Hi Thanh,
I did some (quite heavy) changes on pdftex to support font expansion, so it can be used easily. So far the font expansion feature requires that user must be able to create expanded tfm (eg cmr10+10.tfm). Now font expansion can be used without expanded tfm. One can say:
\font\f=cmr10 \pdffontexpand\f 20 20 5 autoexpand
and pdftex will create those expanded tfm like cmr10+10, cmr10-20, etc. automatically. This also works for virtual fonts (like ptmr8t).
The sources tarball is available at
http://vntex.sourceforge.net/private/thanh/pdftex/pdftex-2004_05_02.tar.bz2
[to Hans Hagen: the djgpp binary of pdfxtex is avail. at the same location]
got it ... works great! this will make hz really usable! i'll see if i can test some big documents. Hans