Hi All,
Sorry for the delay in response.
When you enable the option "Available offline", the file does not get saved on the device.
Currently, there is no option to save scanned PDF locally to the device.
However, you can save the scanned images to photo gallery on your device.
Refer the steps mentioned here: Working with Scanned Documents — Adobe Scan Help.
You may try a workaround to save the scanned PDF locally though.
You can save the file on Drive or Dropbox using the "Share file" option.
Then from there, you can download the PDF to your local folder on the device.
Hope this helps.
You may share your feedback on this with the team here Scan Android Feature Request and Bug Report Form
Let us know if you have any questions.
Regards,
Meenakshi