Letting you enter arbitrary Unicode symbols is not PuTTY's job.  It just
takes what the I/O system hands it.  You want something like the
UnicodeInput system tray addon, which lets you enter any Unicode character
by typing out its hexadecimal code point number.  That's cumbersome for
frequently-used characters, of course, and for that situation you'll
probably want to define your own keyboard layout.


MS keyboard layout creator:

Alternatives: ,

That's all for Windows, which I assume from the PuTTY comment is what the OP
is running.  For Macs, you can use the Unicode keyboard already defined -
holding down Option while typing a hexadecimal code point enters that
Unicode character.  For defining your own keyboard layout, try Ukelele:

On UNIX/Linux I tend to fire up vim, use the control-v + u + hexcode
sequence, and then paste wherever I need.  Hardly elegant, I know, but I'm
not usually on the console running X11, so my options are somewhat
limited.  There are some reportedly nifty XIM solutions, but I have no
experience with them.
Mark J. Reed <[log in to unmask]>