I have "People search results (Page Layout)" page with Content Type = "Welcome Page". I need to drop another people search result web part on this page.
I can see the all web parts but Add button is missing. What to do?
If you are using a custom master page for your search centre then it is probably messing up the layout. Try switching to the standard minimal.master while you edit the page. This should make sure the Add button reappears. You can then switch back to your custom master page when complete.