Acrobat 8 Others can't read typewriter input

When I type with the typewriter tool, it's perfectly legible to me. However, when I send documents to clients, they can't see anything. I used to work around this by making a post-script file and then sending the newly-made PDF. But recently, my clients have reported that they only see little black dots where I input information.
 

 
Thoughts? Thanks in advance.