Laravel表单 - 加载文件字段

I have a file field in my form like this:

<div class="form-group">
    {!! Form::label('pdf', 'PDF Template') !!}
    {!! Form::file('pdf') !!}

    <a href="{{route('download_pdf', ['id' => $template->id])}}">Download current PDF</a>
</div>

I'm using the laravelcollective package to create my forms.

Now on my edit page I would like to load the current file (set the file field). But how can I do this?

You can not set value of the file input.