Also I found this thread. I imagine this is quite important to know also.
Scroll down to the last two posts where it explains.
Here is the jist of what was said...
When you first install the software for your printer choose to install "IRIS" which is the OCR engine for HP Scanning.
"also select "searchable PDF" as file-type. My software defaulted to just "PDF", and that is why I could not select any text in the PDF output files."