... a pdf in cfm page.
It needs to run the standard program (acrobat reader ,...) and then, open my PDF file
Just to be clear, you can't control what happens on the user's computer from the CF server. What you *can* do is serve the pdf in such a way that it will most likely be opened by Acrobat. However, for that to happen, the user must have Acrobat installed on _their_ computer. Most people do have it installed - but again, that's not something you can control.
Anyway, if you already have an _existing_ pdf, use <cfcontent> with the correct mime type to serve the pdf to the user's browser.