Hi. I would like pointers to tools (especially libraries) whether free
or commercial that can be used to convert PDF and postscript files
back to plain text. I am especially interested in those that can
handle documents which contain mathematical or other symbolic
formatted matter within these files to plain text. Do these tools
handle multi column formatted documents? Do they handle documents with
figures, tabular data, charts? I need the list of tools, their prices,
a summary of their capabilities and where to obtain them. Thank you.

Hi,
i give you some adress where you can find good software to do a good conversion.

PDF to what you want!!!! 
http://www.ozgrid.com/Services/convert-pdf.htm
http://www.solidpdf.com/
http://www.softinterface.com/Convert-File-Programs/Convert-File-Program.HTM

PS to PDF and,  PDF to what you want!!!
http://www.ps2pdf.com/convert/convert.htm

hope this helps.   ;-)