     <div class="form-group">
                        <label for="join-name" id="join-label" class="col-form-label">Join files:</label>
                        <p id="pdf-preview-title" class="text-black-50 z-4 text-sm"> Click on a file to preview after
                            upload </p>
                        <input type="file" class="form-control" id="join-name" name="join-name" accept="application/pdf"
                               multiple
                               onchange="previewFiles(eve