How to set up additional FTP user and give them limited access to a directory to upload in plesk

You can do this using the following steps :

login to plesk

Click on domain name--click on webusers and add a webuser.

Add this webuser by the name of directory to which you need the webuser to upload since when you add webuser a directory gets created by its name and user can upload to this directory with webuser name and password and only has access to that directory

Enjoy
Ninad S