To include a pdf file inside a page you have to use
See exmple
<object data="<?php echo $pdf_file['url']; ?>#toolbar=0" type="application/pdf" width="100%" height="600px"> Your mobile browser doesn't have a PDF plugin.Instead you can <a href="<?php echo $pdf_file['url']; ?>#toolbar=0">click here to download the PDF file.</a> </object>