Source := FldSource.Text;
    FileName    := Source + '\*.PDF';
    if FindFirst(FileName,faAnyFile,F) = 0 then
      begin
//        ImageEnView1.;
        ImageEnView1.PdfViewer.LoadFromFile(F.Name);

ImageEnView1.PdfViewer.Enabled := True;
ImageEnView1.IO.LoadFromFilePDF( 'C:\document.pdf' );