Prizmo and PDF files

hello
i have a question regarding Prizmo for Mac.
i have read about it before buying and i believe it's a great one. however, there are certain things i'm not able to do.
i'm trying to scan a pdf file to convert its photos into text like that on Kurzweil for windows. but i'm not able to do that.
have anyone tried to scan a pdf file on Prizmo?
please tell me how
thanks
have a great day :D