i have with text2pdf (tried several  on the internet available versions of this
file) the problem that it extracts only a small amount of the included text. But
as an example "texttopdf" as a part of xpdf gives a much better result but with
the big disadvatage that it can only be used via shell-exec.
It would be useful to have the choice what method is used on an uploaded file to
extract the text.  Best would be if you can define a method bound on the file
extentsion - so you can add other files eg. excel, powerpoint...