discourse/app/assets/stylesheets/common/printer-friendly.scss

@media print {
  /* remove items N/A for print
  ** visual clutter etc. */
  .avatar,
  .topic-avatar,
  header,
  .topic-above-post-stream-outlet.topic-above-post-stream,
  .topic-map,
  .post-menu-area.clearfix,
  div#topic-footer-buttons,
  div#suggested-topics,
  div#progress-topic-wrapper,
  #topic-progress-wrapper,
  div.nums,
  ._flyout,
  .show-topic-admin,
  #topic-progress,
  .quote-controls,
  .topic-status-info,
  div.lazyYT,
  .post-info.edits,
  .post-action,
  .saving-text,
  .draft-text,
  #discourse-modal,
  div.read-state,
  div.read-state.read,
  .edit-topic,
  a.reply-to-tab,
  a.reply-new,
  div.has-pending-posts,
  div.time-gap,
  #bottom,
  #footer,
  .alert-info,
  .badge-category,
  .badge-category-bg,
  .badge-notification.clicks{
    display: none !important;
  }
  /* bottom border to help separate posts */
  div.row {
    border-top: 1px solid #AAA;
  }
  .cooked pre code { max-height: none; }
  #main-outlet { padding: 0 !important; }
  html,body { min-width: 0; height: auto; }
  .lightbox-wrapper img { max-width: 500px !important; height: auto !important; }
  .topic-body { width: auto; margin: 0; padding: 0; float: none; }
  .topic-post article.boxed .select-posts { width: auto; left: auto; right: 0; }
  .gap { width: auto; }
  .gutter { padding: 0; }
  /* restyle div#topic-title */
  #topic-title {
    margin: 0;
    padding: 0;
  }
  #topic-title div div h1 {
    margin: 2.5em 0 0 0;
    padding: 0;
    float: left;
    font-weight: normal;
    font-size: normal;
  }
  a, a:visited {
    color: #DDD;
    font-weight: bold;
  }
  /* hide OP Solved plugin stuff */
  .topic-after-cooked-outlet.solved-panel {
    display: none;
  }
  /* localhost  - MOOT for production */
  .topic-category-outlet.show-topic-category-location,
  div.alert.alert-info.alert-emails-disabled,
  div.profiler-results.profiler-left.profiler-no-controls {
    display: none;
  }
}