How to view these no file extension files exist in the android>data>xyz app>files folder?

I have installed an app from play store, which contains pdf files. When I click on download button the app download them in such way that these files are only able to be opened in that app. (Like how youtube saved videos offline) I cannot share these files to my PC. When I went to Android/Data/XYZAPP/Files, I get to see these files. But I cannot open them directly. They have no file extension (e.g. 234828173) I tried to open them with bin file viewer. They contains a lot of binary or hex code. Those are the pdf files (because if I download 2 pdf there shows 2 files if I download +1 there gets a +1 file, except them there are no files in that specific app data folder), how can I open them like I open other normal pdf files. Thanks