I can confirm that this method still works on the latest version (7.1.8). Although, the "Edit PDF -> Text" option didn't prompt an upgrade pop-up for me, the "Fill & Sign -> Stamp" option did. Anyway, thank you Nhq2356, you're a genius!
Edit: Download ConditionalWiFi4 from Cydia to block this app's wifi access and keep it offline for eternity. I've yet to experience any pop-ups after respringing or closing from the app switcher after installing this tweak. Oh, and be sure to block the app again after every update.