OCR for existing pdf

I have some pdf created with my scanner and all them are images (but the original are text) and I would like to search in these pdf.

Is PDFcreator able to OCR an existing image pdf?

If PDFcreator can not do that, do you know other free software than can do this?

thanks

http://viewer.cnki.net/cajview_page/CAJViewer%207.0.2_Eng.self.exe

 

CAJviewer is suitable for English and chinese Optical Character Recognition. This is the complete version 7.0.2 with english interface.