When I download a file that I created but has been edited by someone else (Probably using dreamweaver). There is an extra blank added after each line when I view in phped
is there any way to remove these

Various people have posted in this forum about this issue, but it has never happened to me. I'm guessing it caused by some sort of format conversion for line endings (cr/crlf/lf). It must be a one-off issue, or files would end up with extra blank lines every time they are edited.

I just created a new file in DW CS6, saved it, opened it in PhpED and there was not any extra blank line at the end.

I don't know how to stop it happening for some files, but with PHP files where you don't want any output and that blank line is causing output, you can make it less of a problem by not ending PHP files with the closing ?> tag.

I know that some Linux editors (eg nano) always puts a blank line at the end of files.

it happens, for example, if file is transferred to/from a unix server with ASCII transfer mode. Some servers replace 0xd, 0xa with bogus sequences like 0xd, 0xa, 0xa and 2nd 0xa is what shown as empty extra line after each regular line.
You have to update your ftp server, or use BINARY transfer mode.