converting PDF to RTF using Automator issue

I am using OS X 10.7.2 and have an issue converting scanned PDFs to RTF using Automator. Now here's the issue: When I scan text from my HP All-In-One C6180 and use HP scan I am able to select this resulting PDF file and place it into my PDF to RTF Convertor made in Automator and I can easily pull out the text and then load it into Word for editing. Not a problem. However, if I use Preview or Image Capture to scan using the HP All-In-One the resulting file will open as a PDF without a problem but if I attempt to convert it to RTF I just end up with an empty file. I can't seem to put my finger on the problem. Any help would be appreciated. Cheers.

 

Possible answer

Not all PDFs contain text.* Some contain only images of text.*Is it possible that Preview and Image capture do just that and only capture images. When I open the PDF in preview (the one captured from HP scan software) I can highlight text; however, this is not possible in those scans created by Preview/Image Capture. Any thoughts on this?