Renaming PDF files with characters

When I send a document out for signing that has a character in the file name such as ' or & the document is being renamed. For example sending a document named O'Brien it is changing the name to O'Brien, and if a file has an & in the name it is changing it to &.  This is also changing in the subject of the email going to clients which doesn't look very professional.  How can this be fixed?