Extracting the text from a pdf file is anything but trivial.
To quote from th iTextSharp tutorial.
"The pdf format is just a canvas where
text and graphics are placed without
any structure information. As such
there aren't any 'iText-objects' in a
PDF file. In each page there will
probably be a number of 'Strings', but
you can't reconstruct a phrase or a
paragraph using these strings. There
are probably a number of lines drawn,
but you can't retrieve a Table-object
based on these lines. In short:
parsing the content of a PDF-file is
NOT POSSIBLE with iText."
There are several commercial applications which claim to be able to do it. Caveat Emptor.
There is also a free software library called Poppler http://poppler.freedesktop.org/ which is used by the pdf viewers of GNOME and KDE. It has a function called pdftotext() but I have no experience with it. It may be your best free option.