El problema es la longitud del texto, hice pruebas con texto más corto y funciona.
Si realmente necesitas todo el texto, también hice pruebas dividiendo el texto en 3 columnas:
El código quedaría así:
Sub COMBINAR_CORRESPONDENCIA()
Dim i As Double
Dim ruta As String
Dim TRAMITE As String
'Dim TEXTO As String
Application.ScreenUpdating = False
ThisWorkbook.Activate
Sheets(2).Name = "GENERAR"
Sheets("GENERAR").Select
Fin = Application.CountA(Sheets("DATOS").Range("A:A"))
'
On Error Resume Next
With CreateObject("shell.application")
ruta = .browseforfolder(0, Titulo, 0).Items.Item.Path
End With: On Error GoTo 0
If ruta = Empty Then
MsgBox "DEBES SELECCIONAR UNA CARPETA DE DESTINO", vbExclamation
Exit Sub
End If
'
For i = 2 To Fin
NOMBRE = Sheets("DATOS").Cells(i, 1)
APELLIDO = Sheets("DATOS").Cells(i, 2)
TRAMITE = Sheets("DATOS").Cells(i, 3)
DEPENDENCIA = Sheets("DATOS").Cells(i, 4)
OFICINA = Sheets("DATOS").Cells(i, 5)
FECHABAJA = Sheets("DATOS").Cells(i, 6)
ANT = Sheets("DATOS").Cells(i, 7)
EDAD = Sheets("DATOS").Cells(i, 8)
FIRMA = Sheets("DATOS").Cells(i, 9)
'
Set h = Sheets("TEXTO")
Set b = h.Columns("A").Find(Sheets("DATOS").Cells(i, 10), LookAt:=xlWhole)
If Not b Is Nothing Then
TEXTO = h.Cells(b.Row, "B")
TEXTO2 = h.Cells(b.Row, "C")
TEXTO3 = h.Cells(b.Row, "D")
End If
'
Call ACTUALIZA
ActiveSheet.Name = Sheets("DATOS").Cells(i, 2) & " " & Sheets("DATOS").Cells(i, 1)
With ActiveSheet
Cells.Replace What:="<TEXTO>", Replacement:=TEXTO, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<TEXTO2>", Replacement:=TEXTO2, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<TEXTO3>", Replacement:=TEXTO3, LookAt:=xlPart, SearchOrder:=xlByRows
Rows("12:12").RowHeight = 400
Rows("12:12").VerticalAlignment = xlTop
Cells.Replace What:="<FECHA>", Replacement:=Format(Date, "mm/dd/yyyy"), LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<NOMBRE>", Replacement:=NOMBRE, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<APELLIDO>", Replacement:=APELLIDO, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<REFERENCIA>", Replacement:=TRAMITE, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<DEPENDENCIA>", Replacement:=DEPENDENCIA, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<OFICINA>", Replacement:=OFICINA, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<ANT>", Replacement:=ANT, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<EDAD>", Replacement:=EDAD, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<FECHABAJA>", Replacement:=FECHABAJA, LookAt:=xlPart, SearchOrder:=xlByRows
Cells.Replace What:="<FIRMA>", Replacement:=FIRMA, LookAt:=xlPart, SearchOrder:=xlByRows
End With
ActiveSheet.ExportAsFixedFormat Type:=xlTypePDF, Filename:= _
ruta & "\" & TRAMITE, Quality:=xlQualityStandard, _
IncludeDocProperties:=False, IgnorePrintAreas:=False, OpenAfterPublish:=False
Sheets(2).Name = "GENERAR"
Next
End Sub