<?php
echo '<a href="FileLink" download="newfilename">Download the pdf</a>';
//It will work for all kind of file.
?>
<?php
// We'll be outputting a PDF
header('Content-Type: application/pdf');
// It will be called downloaded.pdf
header('Content-Disposition: attachment; filename="downloaded.pdf"');
// The PDF source is in original.pdf
readfile('original.pdf');
?>