openproject/app/assets/stylesheets/layout/_print.sass

// -------------------- Media print specific styles --------------------
@media print
  // -------------------- ALL pages --------------------
  .hide-when-print,
  #top-menu,
  #header,
  #main-menu,
  #sidebar,
  #footer,
  #breadcrumb,
  .contextual,
  .other-formats,
  .toolbar-items,
  .ui-helper-hidden-accessible,
  #wiki_add_attachment
    display: none !important

  .notification-box:not(.show-when-print)
    display: none !important

  #main
    background: #fff
    // This counters 'overflow: auto' active in the non print version
    // which will lead to only the first page being printed on some pages.
    // For whatever reasons, all the pages are displayed in the print rendering emulation
    // regardless of the overflow.
    overflow: initial

  #content-wrapper
    width: 99%
    margin: 0
    border: 0
    background: #fff
    overflow: visible !important

  #content-wrapper.hidden-navigation,
  #content.hidden-navigation
    width: 99% !important
    margin-left: 0 !important

  .autoscroll
    overflow-x: visible

  table.list
    margin-top: 0.5em

    th, td
      border: 1px solid #aaa

  // Show dot highlight in print
  // even when bg not enabled
  // not supported in all browsers
  [class^="__hl_"]
    color-adjust: exact
    -webkit-print-color-adjust: exact

  // Sizes from user agent stylesheet
  h1
    font-size: 2em
  h2
    font-size: 1.5em
  h3
    font-size: 1.17em