<form class="article-footnote-form footnote-form" style="margin-top:10px" >
<div class="form-group row">
    <div class="col-md-9">
        <textarea class="form-control" name="footnote" rows="3" autofocus></textarea>
    </div>
    <div class="col-md-3">
        <button class="btn btn-primary" type="submit" id="articleFootnoteBtn">Add Annotation</button>
    </div>
</div>
</form>

$(".article-footnote-form").submit(function(e){
    e.preventDefault();

$("#textareaId").keypress(function (e) {
    if(e.which == 13 && !e.shiftKey) {
        $(this).closest("form").submit();
        e.preventDefault();
        return false;
    }
});