function TForm3.fCreatePDFFile(fInFile,fOutFile: String): boolean;
const
  PDFCompression: array[0..3] of TIOPDFCompression = (ioPDF_RLE, ioPDF_G3FAX2D, ioPDF_G4FAX, ioPDF_JPEG);

var iPageNum : Integer;
    StreamedDoc : TMemoryStream;
begin

  StreamedDoc := TMemoryStream.Create;
  ScanImg.Clear;
  ScanImg.MIO.LoadFromFileTIFF(fInFile) ;
  try
    for iPageNum := 0 to ScanImg.ImageCount - 1 do
    begin
      ScanImg.MIO.Params[iPageNum].PDF_Creator     := 'Company X';
      ScanImg.MIO.Params[iPageNum].PDF_PaperSize   :=  IEStrToPaperSize('A4', iepA4);
      ScanImg.MIO.Params[iPageNum].PDF_Compression := PDFCompression[0];
    end;
    ScanImg.MIO.SaveToStreamPDF(StreamedDoc);
    StreamedDoc.Position := 0;
    StreamedDoc.SaveToFile(fOutFile);
  finally
   StreamedDoc.Free;
   ScanImg.Clear;
  end;
end;

...
  ScanImg.LockUpdate;
  for iPageNum := 0 to ScanImg.ImageCount - 1 do
  begin
    ScanImg.MIO.Params[iPageNum].PDF_Creator     := 'Company X';
    ScanImg.MIO.Params[iPageNum].PDF_PaperSize   :=  IEStrToPaperSize('A4', iepA4);
    ScanImg.MIO.Params[iPageNum].PDF_Compression := PDFCompression[0];
    ScanImg.SelectedImage := iPageNum;
    ScanImg.Proc.Resample(ScanImg.MIO.Params[iPageNum].PDF_PaperWidth, 
                          ScanImg.MIO.Params[iPageNum].PDF_PaperHeight,
                          rfLanczos3, True);
  end;
  ScanImg.UnlockUpdate;
...