For a complete backup, is it enough to copy htdocs and export database?

In general – Yes.

Make sure that the file and directory permissions are appropriate. In case the URL of your website changes, you would have to do a find/replace. Read more about it in the links below. Also, ‘update permalinks’ once you have access to the Dashboard.

References:

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)