This example is based on the write-up here:<br />
<br />
http://birtworld.blogspot.com/2008/09/naming-exported-files-from-birt.html<br />
<br />
The download contains a zip of the source and the jar file. Place the jar file in the viewer WEB-INF/lib and alter the the web.xml
BIRT_FILENAME_GENERATOR_CLASS
my.filename.generator.MyFilenameGenerator
<br />
Add to the viewer url like &__filename=myexportedfilename.pdf