A couple of things:
1. Instead of having a plethora of bookmarks for each replicated item, use just one and insert cross-references to it.
2. To correctly update the bookmarks use code like:
Code:
Private Sub btnInputData_Click()
Application.ScreenUpdating = False
Dim wdDoc As Document
Set wdDoc = ActiveDocument
Call UpdateBookmark(wdDoc, "bmSite", Me.txtSite.Value)
Call UpdateBookmark(wdDoc, "bmclient", Me.txtClient.Value)
Call UpdateBookmark(wdDoc, "bmContactNo", Me.txtContactNumber.Value)
Call UpdateBookmark(wdDoc, "bmProjectManager", Me.txtProjectManager.Value)
Call UpdateBookmark(wdDoc, "bmSupervisor", Me.txtSupervisor.Value)
Call UpdateBookmark(wdDoc, "bmProjectNo", Me.txtProjectNumber.Value)
Call UpdateBookmark(wdDoc, "bmStartDate", Me.DTPicker1.Value)
Call UpdateBookmark(wdDoc, "bmEndDate", Me.DTPicker2.Value)
'
'The rest of your code, from 'Print Sections' onwards, goes here
'
wdDoc.Fields.Update
Set wdDoc = Nothing
Application.ScreenUpdating = True
End Sub
'
Sub UpdateBookmark(wdDoc As Document, BmkNm As String, NewTxt As String)
Dim BmkRng As Range
With wdDoc
If .Bookmarks.Exists(BmkNm) Then
Set BmkRng = .Bookmarks(BmkNm).Range
BmkRng.Text = NewTxt
.Bookmarks.Add BmkNm, BmkRng
End If
End With
Set BmkRng = Nothing
End Sub