To change the web hosting type in the Plese please follow the following settings:-
1) Login to Plesk control panel.
2) Click on "Domains" and then Click on "Control panel" in front of the domain whose files permession you want to change.
3) Click on "Websites and Domains".
4) Click on the "domain name" under whome you want to enable PHP safemode.
5) Click on Check box in front of "PHP safemode" to enable php safemode support.
6) Click on "OK" once you have enabled the PHP safemode checkbox.