silverstripe-framework/admin/client/dist/styles/GridField_print.css

h3,table{
  font-family:Arial,sans-serif;
}

table{
  border-collapse:collapse;
  color:#333;
  font-size:12pt;
}

table th{
  border-bottom:2px solid #333;
  padding:5px 10px;
  font-weight:700;
  text-align:left;
}

table th:first-child{
  padding-left:0;
}

table td{
  border-top:1px solid #aaa;
  border-bottom:1px solid #aaa;
  text-align:left;
  padding:5px 10px;
}

table td:first-child{
  padding-left:0;
}