Select the \uFFFF -> Characters command in the Convert menu to replace all escape sequence in the form of \uFFFF into their actual characters. If you select some text before using this command, only escape sequences in the selection are replaced. Otherwise, all escape sequences in the file are replaced.
The conversion will only be successful if all the characters can be represented in the encoding used by the file. If not, use Convert|Text Encoding to change the encoding before converting the escapes. Escapes that represent characters that are not supported by the file's encoding will not be converted. EditPad will pop up a message to alert you when this happens.
Use the \uFFFF -> Characters command when you actually want to remove the escapes from your file. Do not use this command if you have a file that is pure ASCII with \uFFFF escapes and you want to be able to see the actual characters while keeping Unicode escapes in the file. To do that, use Convert|Text Encoding and select the "ASCII + \uFFFF Unicode Escapes" encoding. This encoding makes EditPad Pro display the actual characters, but keeps the escapes in the file. If you type or paste non-ASCII characters while using the "ASCII + \uFFFF Unicode Escapes" encoding, they will be automatically stored as Unicode escapes in the file.
Convert|Characters -> \uFFFF