GoogleDocs is supported for the following products :-
HP Officejet Pro 8500A e-All-in-One Printer series - A910
HP Officejet 7500 Wide Format All-in-One Printer Series- E910
HP Officejet 6500A e-All-in-One Printer - E710
If you are having issue to add this app for these printers, you can try to reset the web service and reregister.
This will change the eprint address of your printer.
Go to Setup >> Web Services Setup >> Restore Factory Settings
After this step, you can enable the Web Services again by pressing on the Apps icon to complete the registration.
Commented: HP Quick Forms
There is an issue with the notebook paper printing settings and are working on it to correct this.
Thank you for reporting.