I was able to open an existing document that had nothing in it. It was just a word doc I created with a right click. After opening it, I was able to create a connection and be prompted to add data to the word doc. The prompt is controlled with this property (AddToRecentFiles:=True)
However, if you do not have Mail Merge fields defined in your word doc, no data will transfer. Using early binding, I will guess that you could add some fields via VBA. I found some members/methods to do this. It would probably be easier to create a template and use that. Actually, it would be easier to export an Access report and format as word but....
You can add a Mail Merge field by using the Mail Merge tool in the ribbon.
Here is the code to open the doc and create a connection. Once the connection is created, it is built in and does not need to be created a second time. You just need to add the Mail merge fields.
Code:
Dim myWordApp As Word.Application
Dim docNew As Word.Document
Set myWordApp = CreateObject("Word.Application")
myWordApp.Visible = True
Set docNew = myWordApp.Documents.Open("C:\Test\WordDocFolder\TestMailMerge.docx")
With docNew.MailMerge
.MainDocumentType = wdFormLetters
.OpenDataSource _
Name:="C:\Test\AccessFolder\MailMerge_Sample.accdb", _
LinkToSource:=True, AddToRecentFiles:=True, _
Connection:="TABLE tblCustomers"
End With
docNew.Save
docNew.Close
myWordApp.Quit
Set docNew = Nothing
Set myWordApp = Nothing