When creating pages it's common to use commercial trademarks, copyright, umlaut, and other non-keyboard symbols. therefore it's important that you have the means to input these special characters.
ISO Standard codes
PmWiki supports the HTML special character listings by the w3c. W3C Page of Special Character codes ISO standard.
Here are some samples:
For a nice table with all available special characters, see List of Unicode characters at Wikipedia.
Other ways to do it:
Find the "Character Map" utility in your computer's System Tools folder. Click the symbol you're interested in, and note the keystroke information at the bottom of the box. You execute these by holding "Alt" while keying the numbers on the numerical keypad of your keyboard (not the numbers across the top of the board).
© = Alt+0169 = © | ® = Alt+0174 = ® | ° = Alt+0176 = ° (degrees).