1. In the directory

/var/www/vhosts/example.com/conf create a file called vhost.conf

2. Edit the file with a text editor and add the following line:

Documentroot /my/new/DocumentRoot

3. Then execute the following command

/usr/local/psa/admin/sbin/websrvmng -–reconfigure-vhost -–vhost-name=example.com

4. Okay thats it reload the apache webserver

/etc/init.d/apache2 reload