Batch OCR for many PDF files (not already OCRed)?

I use Google Desktop Search (I am on Vista) and not all my PDF files are recognized in my archive folder. It is normal as "PDF files that contain scanned images" are not indexed ( http://desktop.google.com/support/bin/answer.py?hl=en&answer=90651 )

So I would like to OCR many of my PDF files that are not already OCRed. My goal : I give the program a folder and it search alone in the subfolders the PDF files that need to be converted into PDF-OCRed files.

Note: In the past, if a PDF file was password protected, I removed the password with another batch (paying) tool: verypdf.com "pwdremover" http://www.verypdf.com/pwdremover/

Any (not too much expensive) idea ?

I already tried : Finereader 6 pro on xp at the time, but there was no batch processor included... Paperfile paperfile.net which uses Tesseract http://code.google.com/p/tesseract-ocr/ . But the OCR is only PDF to text, not PDF to PDF! There is also another project http://code.google.com/p/ocropus/

Thanks in advance ;)

Adobe Acrobat will process a folder of PDFs and like most Adobe products there's a 30 day trial.
The function is located in the 'Document' menu:

Document > OCR Text Regocnition > Recognise text in multiple files using OCR

from where you can add your folder.

In Acrobat X the function is available as follows:

Tools > Recognize Text > In Multiple Files

Try WatchOCR. It is an open source software package that converts scanned images into text searchable pdfs. It is free and open source and has a nice web interface for remote administration. With the right configuration it be used to create a batch pdf/ocr service for an entire network via smb shares. Unfortunately it is linux only. But you could install it on an old server and then your entire organisation could use it.

If you want to do the same online without installing anything, try PDFCubed.com

Actually, pdfsandwich has been updated within the last year and was not at all difficult for me to install in Linux Mint. The results it gives are inferior to Adobe Acrobat, but it's the only workable solution I've found in Linux so far.