Either use a pdf ActiveX control or the Web Browser control.
Here's some sample code for the Web Browser controlbecause it isn't apparent how to use the navigate method:
Private Sub cmdNavigate_Click()
If Not IsNull(Me.txtURL) Then
With Me.ActiveXCtl0
.Navigate Me.txtURL
End With
End If
End Sub
cmdNavigate is a button which is using the path in txtURL as a hyperlink
substitute. If you put the full path to the pdf file in txtURL it will open
it within the Access form's IE control.