I have a custom plugin that creates an input field under each post, that allows users to upload PDF files.

$html .= '<input accept="application/pdf" type="file" id="wp_custom_attachment" name="wp_custom_attachment" value="" size="25">';

I am using wp_upload_bits and wp_insert_attachment to upload the file:

if(!empty($_FILES)) {
  if ( !empty($_FILES['wp_custom_attachment']['name'])) {
    $uploaded_anexa = wp_upload_bits($_FILES['wp_custom_attachment']['name'], null, file_get_contents($_FILES['wp_custom_attachment']['tmp_name']));
    $uploaded_anexa_location =  trailingslashit ( $wp_upload_dir['path'] ) . $_FILES['wp_custom_attachment']['name'];  
    $attachment_anexa = array(
      guid' => trailingslashit ($wp_upload_dir['url']) . basename( $uploaded_anexa_location ),
     'post_type' => 'attachment',
     'post_mime_type' => $_FILES['wp_custom_attachment']['type'],
     'post_title' => preg_replace('/\.[^.]+$/', '', basename( $_FILES['wp_custom_attachment']['name'] )),
     'post_content' => $_POST['_wpd_sub_title_title'],
     'post_status' => 'inherit',
     'post_category' => array( 0, $id ),
     'post_excerpt' => $numar_inregistrare,
    );
    $attach_id = wp_insert_attachment( $attachment_anexa, $uploaded_anexa_location, 37);
    array_push($files, $uploaded_anexa_location);
    
  }

The problem is that this code only works with certain PDF files. For instance, if I try to upload a PDF file created with Word -> Create PDF I get this error:

Warning: fopen(/var/www/html/wp-content/uploads/2022/01/Anexa dispozitie.pdf): failed to open stream: No such file or directory in /var/www/html/wp-content/plugins/print-post-to-pdf/FPDI/src/PdfParser/StreamReader.php on line 42 Fatal error: Uncaught InvalidArgumentException: No stream given. 

If I convert the file with Mac OS's Preview and generate a new PDF (with the same content) it works just fine and the file gets uploaded.

Can you please give me your opinions on how I can address this issue? Thanks!