From which OS you start ftp ? On linux you can run chmod from ftp.
List available commands depend from ftp client. Try use another ftp-client.
I am running the script in windows 8.
Set the file permissions properly before ftp'ing.
chmod is a unix/linux command.
For a .pdf file, linux/unix 777 privilege looks wrong anyway. 7 denotes read/write/execute and for owner, group, world it would be 777.
At most a pdf needs read/write which in unix would be 6, so chmod 666 file.pdf would grant read/write to owner, group, world.
Anyway as said set the appropriate, read/write file permissions in windows on the file BEFORE ftp'ing the file to anywhere.
Perhaps the file already has the correct permissions so you don't need to try and change them anyway.
As stated elsewhere, other ftp clients offer file permission functionality in the client itself, filezilla, for example.
Here is some additional info that may help.
Solaris proftpd.conf has option for umask.
Files uploaded to a proftpd server will never have the execute permission enabled by default
The default in /etc/proftpd.conf is :
A better option is to use sftp | scp (ssh ) which is more secure and will preserve permissions of the file transferred.