Hi, I cannot find an option to set a default pdf application on redmi note 11 pro 5G. each time I open a pdf file, I have to choose an app and no option for using default one or remember this choice !
Happening to me with Redmi Note 11s, sadly this seems to be a MIUI 13 bug they won't fix until next firmware updates for our devices. PDF managing is messed up. Disappointed!
You can to disable "MIUI optimization" from "Developer options", then you must open a pdf file and choose your default application, after you set you default app, I would recommend enabling "MIUI optimization" to avoid bugs in your phone.
sorry my bad english, I am from Brasil