Chrome has "Failed to load PDF document" error message on inline PDFs

I've been wrestling with this same issue. This is as close as I got to consistent results across browsers. I think that the reason you could be having problems is if some PDF's are too large for readfile() to handle correctly. Try this:

$file = "path_to_file";
$fp = fopen($file, "r") ;

header("Cache-Control: maxage=1");
header("Pragma: public");
header("Content-type: application/pdf");
header("Content-Disposition: inline; filename=".$myFileName."");
header("Content-Description: PHP Generated Data");
header("Content-Transfer-Encoding: binary");
header('Content-Length:' . filesize($file));
ob_clean();
flush();
while (!feof($fp)) {
   $buff = fread($fp, 1024);
   print $buff;
}
exit;