The latest Umbraco versions have the functionality to show or hide submit buttons using conditions. But for my case it doesn't work. For other field I have fieldsets and while iterating over fieldsets I do this

var hideFieldWhenRendering = f.HasCondition && f.ConditionActionType == FieldConditionActionType.Show;

and add class on the div like this @{ if (hideFieldWhenRendering) { } }

But submit buttons is not a part of fieldset and I don't find a way to check attribute HasCondition for it. My html for submit looks like this

<div class="umbraco-forms-navigation row-fluid">

<div class="col-md-12">
    @if (Model.IsMultiPage)
    {
        if (!Model.IsFirstPage)
        {
            <input class="btn prev cancel"
                   type="submit"
                   value="@Model.PreviousCaption"
                   name="__prev"
                   formnovalidate
                   data-form-navigate="prev"
                   data-umb="prev-forms-form" />
        }

        if (!Model.IsLastPage)
        {
            <input type="submit"
                   class="btn next"
                   value="@Model.NextCaption"
                   name="__next"
                   data-form-navigate="next"
                   data-umb="next-forms-form" />
        }

        if (Model.IsLastPage)
        {
            <input type="submit"
                   class="btn primary"
                   value="@Model.SubmitCaption"
                   name="__next"
                   data-form-navigate="next"
                   data-umb="submit-forms-form" />
        }
    }
    else
    {
        <div class='input -right submit-button'>
            <input type='submit' name="submitbtn" class='button -cta' id='submit' value='@Model.SubmitCaption'>
        </div>
    }
</div>