For setting permissions on a file in ColdFusion use the optional mode attribute of cffile with the octal values of UNIX chmod command.
<cffile action="write" destination="#fileToWrite#" mode=777>
This applies to Unix/Linux only.
If this is about files uploaded to your server and you have access to your ftp admin / config files, then you probably would want to modify the upload mask to adjust permissions of the files uploaded.
If you download the files yourself manually, then you would have to put it in a folder where coldfusion at least has read access, or tell your ftp client to store the file accessible for cf.