This is the solution I found, it is from Robb92014:
"Same problem here. Easy solution - just use Preview when you use the HP 8600 to scan. Simply put your docs to be scanned on the feeder and Preview/file/import from officejet pro 8600. A screen then lets you toggle on/off various odds & ends, such as PDF vs. TIFF; save all scans as one document; duplex; etc.
Works easily."