Nuance.com (nee Scansoft) carries lots of scanner software. PaperPort is great but it costs more than lots of scanners and it doesn't work with some brands/models.. So I'd recommend following HP's advice if you can DL the stuff for your scanner - looks like you can order a replacement software CD.
I have software that can turn any printable file into a .PDF - it's free. So if you can't DL the software you need (scans directly to PDF), if you can scan to an image file or OCR the scan, you still have a way to get it to PDF. It's called Primo PDF and you download it direct from their site.
.bh.