Re: how can I print A9 or half-fold card envelope on HP 7520 All in One printer?

Sounds like you are wanting to print on custom media sizes, is that about right? I would recommend this guide for assigning an alternate driver which might have that feature and if you cannot find it in the two suggested printer models I would look at that Deskjet 9800 driver.

http://h30434.www3.hp.com/t5/Printer-All-in-One-Software-Drivers-e-g-Windows-8/How-to-Assign-Alternate-Print-Drivers-in-Different-Versions/td-p/1957011

Let me know how that goes! 

-Spencer 

Have a wonderful day and a fantastic weekend!