The "official" answer from HP's website is to use the Windows Fax and Scan software that came with Windows 7. This solution, however, at least has the following issues:
- I can no longer connect my HP printer to the router and use it as a network scanner because Windows Fax and Scan will not recognize it as a scanner (printing is okay)
- Windows Fax and Scan does not let you save scanned document in PDF format but TIFF only
- Unless you use the document feeder of the printer, you cannot scan multiple pages at one shot. Instead, you have to scan the pages one-by-one, save them as separate files and merge them together, which is a big hassle.
I exchanged a few emails with HP support but they would not help me as the warranty of my printer has already expired. Guess what, when it is time for me to get a new printer, I will definitely not buy from HP.
The Microsoft Office Document Imaging software that comes with Microsoft Office can actually scan multiple pages in one shot but then I discovered that it is deprecated (no longer available) in Office 2010!
So, I tried to look for a third-party solution and found a software named A-PDF Image to PDF. I downloaded its trial version and finally I can scan multiple pages manually without the feeder as a single PDF file. It is not free (the trial version will put a watermark at the upper left corner on the first page) but it has a better interface and a lot more features than the HP scan software that I have been using in Windows XP and Vista.
Hopefully this is useful to others who got screwed by HP's All-In-One printers :P