Create a separate "ftpgroup" group and an "ftpuser" user:

Commiting changes
Any changes you make to the virtual users won't be recognized by Pure-FTPd until you commit the changes in /etc/pureftpd.passwd into a PureDB file/etc/pureftpd.pdb:

There's no need to restart the pure-ftpd server to commit changes.
Enabled virtual user support
Assuming that Pure-FTPd has been compiled with virtual user support (./configure --with-puredb), add this switch to your startup command (i.e. /service/pure-ftpd/run):

All maintenance of virtual users will be handled with the pure-pw command:

• Add a user:
  
  pure-pw useradd joe -u ftpuser -d /home/ftpusers/joe
• Delete a user:
  
  pure-pw userdel joe
• Change a password:
  
  pure-pw passwd joe

Anonymous User with Virtual Users
You must have a *system* account called 'ftp' that has a home directory, but it does not need a shell. /etc/passwd should have that account, such as