docbook message

Subject: Fwd: How do I embed fonts in a PDF?

From: "Sheldon Plankton" <sheldon.plankton@gmail.com>
To: docbook@lists.oasis-open.org
Date: Fri, 14 Sep 2007 23:19:43 -0700

---------- Forwarded message ----------
From: Sheldon Plankton <sheldon.plankton@gmail.com>
Date: Sep 14, 2007 11:15 PM
Subject: How do I embed fonts in a PDF?
To: docbook-apps@lists.oasis-open.org

Hi,

I generated my PDF book with docbook and tried to upload it to lulu.com.
Lulu.com reject my upload stating that ...

Your document could not be created: This font is not embedded: Helvetica-Bold ( How do I embed fonts?)
This font is not embedded: Helvetica ( How do I embed fonts?)
This font is not embedded: Times-Roman ( How do I embed fonts?)

... what are they talking about and what can I do in my custom style sheet to fix it?

Thanks
Plankton