A:Answer It was in the Specifications that were listed under the printer. BestBuy could have answered it for you in a chat if you have access to that.
If your Legal Size is 8.5 inches by 14 inches, then YES, it does print Legal Size. Check the link and look under Specifications. (See below)
https://www.bestbuy.com/site/hp-officejet-pro-8720-wireless-all-in-one-printer/5623289.p?skuId=5623289
Paper Info
Automatic Document Feeder Capacity
50 sheets
Maximum Document Length
14 inches
Maximum Document Width
8.5 inches
Supported Paper Sizes
Letter, Legal, Government Legal, Executive, Statement, Envelope, Card, Custom
Paper Handling
ADF-50 sheets, Input tray-250 sheets, Output tray-150 sheets
Compatible Media Types
Plain paper, Light/Recycled, Inkjet Hagaki, Matte and Glossy Inkjet Paper, Plain Paper, Thick
'Hope that you helps you.