[O] eliminating blocked tasks from printed agenda

[Mike Ashley]

I am having a configuration problem I was hoping to get some help
with. I have a simple agenda configuration file that looks like this.

(setq org-agenda-custom-commands
  '(("o" "Office tasks"
      tags-todo "OFFICE"
      nil
      ("~/agenda.pdf"))))

And I have the custom variable org-agenda-dim-blocked-tasks set to the
symbol invisible.

It does what I expect when I build the agenda in buffer.  Blocked
tasks are hidden.  However, when I export the agenda to PDF, blocked
tasks are included in the agenda.  

Is there anything I can configure so that the exported agenda does not
include blocked tasks?

Thank you for the help.