Yes.
You’re particularly interested in the files cert.pem, config.xml, key.pem. These files are crucial. You may however back up the entire directory, just in case (possible changes to the files inside directory in the future, etc).
Just be aware that files named like <number>.ldb (inside a index-*.db folder) contain the database. The database can be rebuild without much trouble and restoring the database from a backup can cause errors, so it might be best to not restore it after a re-install.