Show uploaded pdf files dynamically and filter by month name

I want to show PDFs for a specific WordPress page that filters by (month)name. e.g: check the current month (October) and show october.pdf. All the PDF documents will upload from the admin panel and I want to show the current month PDF in a page in the front-end dynamically.

Here is the code that I tried:

<?php

//Get the full textual representation of current month in lower case
$months = strtolower (date('F'));


//Convert the current month name to PDF file location
$filename = '/wp-content/uploads/2020/10/'. $months.'.pdf';


if (file_exists($filename)) {
    // Header content type 
    header("Content-type: application/pdf");
    header("Content-Length: " . filesize($filename));

    // Send the file to the browser. 
    readfile($filename);


} else {
    // echo 'False ';
    // die;
}

?>