Option Explicit

Sub Macro1()
Dim strFname As String
Dim oDoc As Document
    strFname = BrowseForFile("Select the PDF file to open")
    If strFname = vbNullString Then GoTo lbl_Exit
    Set oDoc = Documents.Open(strFname)
    'do stuff with odoc
lbl_Exit:
    Exit Sub
End Sub

Function BrowseForFile(Optional strTitle As String) As String
'Graham Mayor - http://www.gmayor.com
'strTitle is the title of the dialog box
'Set bExcel value to True to filter the dialog to show Excel files
'The default is to show Word files
Dim fDialog As FileDialog
    On Error GoTo err_handler
    Set fDialog = Application.FileDialog(msoFileDialogFilePicker)
    With fDialog
        .Title = strTitle
        .AllowMultiSelect = False
        .Filters.Clear
        .Filters.Add "Adobe PDF files", "*.pdf"
        .InitialView = msoFileDialogViewList
        If .Show <> -1 Then GoTo err_handler:
        BrowseForFile = fDialog.SelectedItems.Item(1)
    End With
lbl_Exit:
    Exit Function
err_handler:
    BrowseForFile = vbNullString
    Resume lbl_Exit
End Function