PrinceXML publishes a series of CSS stylesheets  each declaring a set of fonts using @font-face. 
Web authors can then easily @import (some of) those stylesheets, allowing them to use those fonts in their site even if the visitor doesn't have the fonts installed.
(The visitor does need to be using a browser supporting the spec , such as Firefox 3.5+ or Safari 3.1+.)
Unfortunately, there's no stylesheet declaring the DejaVu fonts. You should publish one. If the DejaVu project controls the canonical example of such a stylesheet, you can ensure that it includes updates and new fonts.