HP Deskjet 6840 Color Inkjet Printer - Manual (Page 139)

2. Load the photo paper correctly in the In tray.
3. Verify that the paper guides fit firmly against the media.
Printout has an unwanted border
For most photo paper types
If the printout has an unwanted border, then align the print cartridges .
For photo paper with a tear-off tab
If the border appears below the tear-off tab, then remove the tab.
If the border appears above the tear-off tab, then align the print cartridges .
HP Deskjet 6800 series printer User's Guide
139