What you need is Optical Character Recognition software or OCR. If HP does not already come with an OCR option in the software installation package then you will need to look elsewhere.
OCR for PDF documents can be aquired through Adobe products. Most Adobe products like Acrobat have a feature that allows them to create OCR PDF files.
There are also free OCR alternatives on the web. For example: http://www.free-ocr.com/ allows you to upload image files and converts them to text. You need to follow the websites guidelines such as 2MB file limit and 5000 pixel wide/high and 10 images per hour.