Restoring App Data from Backup How can I restore one app’s data from an encrypted iTunes backup (iOS 11.3.1) to the same app on iOS 11.4? I deleted the Readdle Documents app by mistake and I had some files in it I would like back. I would prefer free or open source tools if possible. I am using Windows 10.

(I don’t believe this is possible in iTunes. I tried iMacTools’ iBackup Viewer, and it only extracted what seemed to be placeholders for my files. (See answer below.))
It turns out that the files stored in Readdle Documents are not stored in the normal location where apps store their Documents and Data. (This may be because Readdle Documents lists itself as a Cloud Storage Provider.) Using the Tree View of the Raw Files section of iBackup Viewer, I was able to export the files in the AppDomainGroup-group.com.readdle.documents/File Provider Storage folder and reupload the files into Readdle Documents through its WebDAV feature.

I downloaded iBackup Viewer from https://www.imactools.com/iphonebackupviewer/.