Hello, Peggy is back. smirk
It scanned in color to the memory card (actually give me the option of color or grayscale, along with resolution, paper size, etc.)
So it gave different options going to the card? That kind of tells me that it's something in the scanner software on the computer telling the printer what its capabilities are.

If you pull out the Ethernet cable, make sure it's not connecting wirelessly either, it will probably tell you no PC connected, which means it's looking for the software to make it's decision on what to do. Maybe when the built in printer scanning software commingles with the PC software it's not seeing the same Save As options as the built in printer software gives when going to the card.

Acrobat only opens the file, it shouldn't affect output from a device since Acrobat X doesn't install a printer driver. You have a clean system, we didn't do a migration so there isn't any Adobe 9 or earlier PDF print driver. Is there a setting in the HP software that involves Acrobat such as setting the default app to open a PDF scan in?

A way to test Acrobat is to uninstall Acrobat and see if that's affecting it.
Like I said earlier, it's not a hill to die on
I heard, your voice carries, but you posted a challenge. grin