Here is a site that address this:
Sent by Joe Cooperrider on 10/20/2002 06:00:56 PM:
I am trying to write a function that displays a pdf file. I have a variable to store the passed file name. I am then trying to display the file with the following:
HML_OUT="Content type: application/pdf"+chr(10)+chr(10)+readfile(m.lc_filename)
It works on a couple of files but on 99% of files it returns the pdf code without launching Acrobat.