 Shares of PTC Inc. PTC, -1.26 fell 1.5 in midday trading Wednesday, after one of the product management software companys largest shareholders, Rockwell Automation Inc. ROK, 0.76 , said it planned to sell some shares. In an form 13D filed before the open, Rockwell said it owned 10.57 million PTC shares, or 9.04 of the shares outstanding, which was enough to make Rockwell the second-largest shareholder, according to FactSet data. 