I suppose you are talking about PDF Explorer. If yes, you are in the wrong forum section, this one is for PDF-ShellTools. Anyhow...
However we just had the free trial of your software and now we can't download the full version.
If you want to download the commercial version you just need to buy the license. To manage 20,0000 PDFs its really a good investment
If you could tell me how you get a hold of the ProducedBy property I could probably write a program to just do that.
Google for it. Search for "extract PDF metadata" or something related, and I'm sure you are going to find your solution. Even so, if you want to develop the functionality from scratch, without the help of already available libraries/tools, prepare yourself to write many lines of code to deal with the exotic PDF internal structure.
Take a look also to the PDF reference documentation
http://www.adobe.com/devnet/pdf/pdf_reference.html