How to recover files
What have you uninstalled?
Adobe acrobat reader
Then you have lost also the files stored in the app.
FWIW, you can recover the application by simply reinstalling it. If you have an Adobe ID and stored files in the Adobe Document Cloud, once you login, those files will again be available to you.
However, if you stored files on your iOS device itself, uninstalling the application also deletes all the files associated with the application's workspace, including all locally-stored PDF files. To be very clear, that isn't something under Adobe's control; that is Apple's mishagoss! The uninstallation is totally under the control of iOS (iPhone) or iPadOS (iPad).
To be safe, you should frequently backup your device and/or regularly make copies of your local files on one or another cloud-based file servers (including the Adobe Document Cloud).