Word to PDF random character errors

To Whom It May Concern-

When converting documents from word to PDF, it appears some characters (i.e. numbers, greater than or less than signs, and hyphens) do not convert correctly.  This also seems to happen at random in the documents so sometimes only one "9" will appear incorrectly but the others are all showing correctly.  Is there a way to tell when this happens or prevent it from happening?

Thanks!