Instruction to clear the instances:

1. Run cmd, as user (the one who is used to run the server service), 
   run the command: 

   sqllocaldb stop "FineReaderServer"
sqllocaldb delete "FineReaderServer"

2. Run cmd as System (there are various ways to do this, for example Process Hacker third-party software:
   ) 
   run the command: 
   sqllocaldb d "FineReaderServer"

3. Delete following registry branches:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server Local DB\Shared Instances\FineReaderServer
   Search through HKEY_USERS branch using the keyword: UserInstances
   Check that found instances are related to localdb (there should be a reference:
   
   Found branches may look like this:
   HKEY_USERS \.DEFAULT\Software\Microsoft\Microsoft SQL Server\UserInstances Or HKEY_USERS\<<User under which service server is running>>\Software\Microsoft\Microsoft SQL Server\UserInstances  
   Delete instances whose DataDirectory key contains "FineReader Server".

4. Delete all files from following folders:
   %SYSTEMROOT%\System32\config\systemprofile\AppData\Local\Microsoft\Microsoft SQL Server Local DB\Instances\FineReaderServer
   %SYSTEMROOT%\SysWOW64\config\systemprofile\AppData\Local\Microsoft\Microsoft SQL Server Local DB\Instances\FineReaderServer
   %localappdata%\Microsoft\Microsoft SQL Server Local DB\Instances\FineReaderServer

5. Delete all files from %programdata%/ABBYY FineReader Server 14.0\Database\