Macro - Word Mail Merge into separate documents as PDF's

Hi, I've used the below listed macro for years with out issue, and today I receive a Run-time error "5631" and for the life of me am not able to fix it. I modified the .FirstRecord and .LastRecord code but it will only PDF the first document and not all 350+ I need. Any suggestions? I am by no means any sort of an expert.

Thanks!! Tanja

Sub Merge_to_pdf() '
' merge1record_at_a_time Macro
'
'
    Dim fd As FileDialog


    'Create a FileDialog object as a Folder Picker dialog box.
    Set fd = Application.FileDialog(msoFileDialogFolderPicker)
    With fd


        'Use the Show method to display the Folder Picker dialog box and return the user's action.
        'The user pressed the button.
        If .Show = -1 Then
                For Each vrtSelectedItem In .SelectedItems


                'vrtSelectedItem is aString that contains the path of each selected item.
                'You can use any file I/O functions that you want to work with this path.
                'This example displays the path in a message box.
        SelectedPath = vrtSelectedItem


        Next vrtSelectedItem


        Else
        MsgBox ("No Directory Selected.  Exiting")
        Exit Sub
        End If
    End With


    'Set the object variable to Nothing.
    Set fd = Nothing


Application.ScreenUpdating = False


MainDoc = ActiveDocument.Name
    ChangeFileOpenDirectory SelectedPath
    For i = 1 To ActiveDocument.MailMerge.DataSource.RecordCount
        With ActiveDocument.MailMerge
            .Destination = wdSendToNewDocument
            .SuppressBlankLines = True
            With .DataSource
                .FirstRecord = i
                .LastRecord = i
                .ActiveRecord = i
                docName = .DataFields("Employee_Name").Value & " PSU" & ".pdf"       ' ADDED CODE
            End With
            .Execute Pause:=False
    Application.ScreenUpdating = False
            
        End With
    ActiveDocument.ExportAsFixedFormat OutputFileName:=docName, _
        ExportFormat:=wdExportFormatPDF, OpenAfterExport:=False, OptimizeFor:= _
        wdExportOptimizeForPrint, Range:=wdExportAllDocument, From:=1, To:=1, _
        Item:=wdExportDocumentContent, IncludeDocProps:=True, KeepIRM:=True, _
        CreateBookmarks:=wdExportCreateNoBookmarks, DocStructureTags:=True, _
        BitmapMissingFonts:=True, UseISO19005_1:=False
    ActiveWindow.Close SaveChanges:=False
    

    Next i
Application.ScreenUpdating = True

End Sub

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