1. In GTM, add new tag type Custom HTML
2. In HTML editor, paste provided tag
3. Choose Trigger: All Pages
4. Save, Submit and Publish the new version.
Given below is a demo tag for GTM integration:
<script>window.addPAC = function (c, e) { document.cookie = 'PAC=' + c + ';' + e + ';' }</script>