<?php

$filePath = 'file/example.pdf';

if (!file_exists($filePath)) {
    echo "The file $filePath does not exist";
    die();
}

$filename="example.pdf";
header('Content-type:application/pdf');
header('Content-disposition: inline; filename="'.$filename.'"');
header('content-Transfer-Encoding:binary');
header('Accept-Ranges:bytes');

readfile($filePath);
?>

you can try with this code

I would go with what @CBroe suggested: update your code with target to open the link (your PDF) in a new window/tab:

$pdf_title_str = '<a target="_blank" href="' . esc_url($file_url) . '"' . esc_attr($open_target_str . $nofollow_tag_str) . '  title="' . esc_attr($pdf_item_obj_title) . '" class="bsk-pdfm-pdf-link-for-title pdf-id-' . esc_attr($pdf_item_obj->id) . '">' . $pdf_title_str . '</a>';