It is possible to convert fonts from legacy 8-bit encodings to Unicode (in effect re-encoding the old font as a Unicode font). It is also possible to convert existing text in a legacy font to Unicode.
An explanation of how to convert fonts is given at http://billposer.org/Linguistics/Computation/Reencoding/HowTo.html
The conversion of documents is a more involved process. Several years ago, RIFAL undertook a project in several African countries to develop programs to do this. [more info coming]
