In light of the almost non-existent documentation for a very
useful tool, I hereby publish the necessary information
(gleaned from Mike Shea and multitudenous web sites) to
get Word (or any other app. that supports ActiveX controls)
to programmatically print a PDF without using DDE (the
Shell command) and without user intervention.

1) Adobe Acrobat Reader 4 or 5 must be installed on PC.
2) Add reference to "Acrobat Controls for ActiveX" (this is
the pdf.tlb file located by default in C:Program
FilesAdobeAcrobat 5.0ReaderActiveX (or 4.0 if you have
that version).
3) Add the control to the IDE control toolbox
4) Drop an instance of the control onto a userform (for this
example named frmPDF). This instance is named Pdf1 by
5) In the Userform Initialize event code this:

Private Sub UserForm_Initialize()
Pdf1.src = strPDFName
End Sub

where strPDFName is the fullname or URL of PDF file.

In your VBA code module code this:

Public strPDFName As String
Sub TestPDF()
strPDFName = "D:std204.pdf"
Load frmPDF
End Sub

Run TestPDF