Most FTP clients provide the option to change file / folder permissions, a.k.a. attributes.
For example, setting a file or folder permission in FileZilla is very easy. Select a file, then right click on it. A menu will appear and you will need to choose "File Attributes"
A pop-up will appear with options available for all permissions of each group. You simply have to check the boxes or enter the numbered permissions that you require.
With CuteFTP, navigate the "remote" directory to the directory that contains the file for which you need to set permissions. Right-click on the file whose permissions you want to modify.
From the menu, select "Change File Attributes". This will bring up a window allowing you to specify unix permissions.