Hi Viegas73,
Great question! If you're looking to scan directly from your HP DeskJet to PDF, you'll need to use either software included with the scanner or Adobe Acrobat. Adobe offers a free 30-day trial of Acrobat, if you'd like to see how it works for you. See www.adobe.com/products/acrobat.html.
Please let us know how it goes.
Best,
Sara