pyme,
How are you doing?
Open the software and go to (I believe it is) Settings > Scan Settings and Preferences (or something like that) and see if it is set to only scan one page at a time.
I would also recommend using a different software application run and use (edit, etc) your scans than the HP DIM. Adobe Acrobat allows you to capture scans and then build multiple PDF files, have it all saved to one, etc.You could even scan say 10 pages and then put pages 2, 4, 7-9 as one PDF and then 1-8 as another, etc. Bascially whatever you want to do, you can do with that software.
Also - go here:
http://h10025.www1.hp.com/ewfrf/wc/softwareCategory?product=3441026&lc=en&cc=us&dlc=en&submit.y=0&submit.x=0&lang=en&cc=usSelect your O/S and download the FULL FEATURE software/driver.
Hope this helps,
Kevin