Acrobat cannot read .FDF written with Excel VBA

I exported a PDF with form fields in FDF and wrote a sub to output another FDF verbatim, with cell values for the form field values. If I edit the FDF in a text editor and change the values, Acrobat can read the file just fine, but the file output with VBA throws an error:

Adobe could not open whatever.fdf because it is either not a supported file type or because the file has been damaged

I've tried two different types of line breaks, I've tried a similar sub with xfdf formatting which is slightly different with the same results.

Sub something()

Dim sht As Worksheet
Set sht = Sheets("owssvr")

Dim lastrow As Integer
lastrow = sht.Cells(sht.Rows.Count, "A").End(xlUp).Row

Dim fso As Object
Set fso = CreateObject("Scripting.FileSystemObject")
Dim Fileout As Object

Dim x As Integer
For x = 2 To lastrow
    Set Fileout = fso.CreateTextFile("C:\Users\blabla\" & x & ".fdf", True, True)
                Fileout.Write "%FDF-1.2" & vbCrLf & _
                "%âãÏÓ" & vbCrLf & _
                "1 0 obj" & vbCrLf & _
                "<</FDF<</F(MyDocument.pdf)/Fields[<</T(Adobe Form Field)/V(" & sht.Range("U" & x) & ")>>]/ID[<4ED54800AC4A3D41ABE4F4C7B12A3D23><609E705B7532334B8F914CFF4C09F2A0>]/UF(MyDocument.pdf)>>/Type/Catalog>>" & vbCrLf & _
                "endobj" & vbCrLf & _
                "trailer" & vbCrLf & _
                "<</Root 1 0 R>>" & vbCrLf & _
                "%%EOF" & vbCrLf
Fileout.Close

Next x

End Sub

Solution

As much as I want to leave this open in hopes somebody figures out WHY VBA is screwing up the unicode, my problem can be solved without invoking fso at all and just using FreeFile and string replace on an original FDF

Sub blabla()

Dim objAcroApp As Acrobat.AcroApp
Dim objAcroAVDoc As Acrobat.AcroAVDoc
Dim objAcroPDDoc As Acrobat.AcroPDDoc
Dim jsObj As Object
Dim boResult As Boolean
Dim oldPDF As String
Dim NewFilePath As String

    Dim sTemp As String
    Dim iFileNum As Integer
    Dim oldFDF As String
    Dim i As Integer
    Dim lastRow As Integer
    Dim sht As Worksheet
    Set sht = Sheets("owssvr")

    With sht
        lastRow = .Range("A" & .Rows.Count).End(xlUp).Row
    End With

    For i = 2 To lastRow

    oldPDF = "\mydoc.pdf"
    oldFDF = "\mydoc_data.fdf"
    newPDF = "\" & i & ".pdf"

    iFileNum = FreeFile
    Open oldFDF For Input As iFileNum

    Do Until EOF(iFileNum)
    Line Input #iFileNum, sBuf
    sTemp = sTemp & vbCrLf
    Loop
    Close iFileNum

    sTemp = Replace(sTemp, "<</T(some form field)/V( )>>", "<</T(some form field)/V(" & sht.Range("E" & i) & ")>>")

    iFileNum = FreeFile
    oldFDF = "\" & i & ".fdf"
    Open oldFDF For Output As iFileNum

    Print #iFileNum, sTemp

    Close iFileNum

            Set objAcroApp = CreateObject("AcroExch.App")
            Set objAcroAVDoc = CreateObject("AcroExch.AVDoc")
            boResult = objAcroAVDoc.Open(oldPDF, "")
            Set objAcroPDDoc = objAcroAVDoc.GetPDDoc
            Set jsObj = objAcroPDDoc.GetJSObject
            jsObj.ImportAnFDF oldFDF
            jsObj.SaveAs newPDF
            boResult = objAcroAVDoc.Close(True)
            boResult = objAcroApp.Exit

Next i


End Sub