program.css.scss

header.program-pdf {
	table.items {
		.tr {
			background-color: inherit;
			background-image: none;
		}
	}
}

program.pfd.erb

<header class="program-pdf">
      <h2><%= @conference.date_finish>Time.current ? t(:preliminary_program_of_the_conference) : t(:program_of_the_conference)%></h2>
      <h3>"<%= @conference.title %>"</h3>
      <h4><%= date_start_finish_for(@conference) %></h4>
      <table class="items">
        <tr>
        <% @sponsors.map do |sponsor| %>
          <td><%= sponsor.first %>:</td>
          <% sponsor.second.map do |sponsor| %>
            <td><%= pdf_image_tag(sponsor.logo.to_s, width: "100") if sponsor.logo.present? %></td>
          <%end%>
        </tr>
        <%end%>
      </table>
    </header>