$url='http://remote.com/myfile.pdf';
$local='/path/to/local/file.pdf';
file_put_contents($local, file_get_contents($url));
$remoteUrl = "http://remote.com/file.pdf";
$userAgent = 'Googlebot/2.1 (http://www.googlebot.com/bot.html)';
$ch = curl_init($tremoteUrl);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_BINARYTRANSFER, true);
curl_setopt($ch, CURLOPT_USERAGENT, $userAgent);
$output = curl_exec($ch);
$fh = fopen("file.pdf", 'w');
fwrite($fh, $output);
fclose($fh);