Now – if you’ve accidentally stumbled upon this blog post you have probably already stumbled upon this MSDN article: https://msdn.microsoft.com/en-us/library/office/jj713593.aspx
Here’s the steps..
1. Open up your site in SharePoint Designer
2. Navigate to your List and find the form which you want to add the People Picker control to – NewForm, EditForm, Editifs, etc..
3. Right click that form and select Edit in Advanced Mode
4. Locate the PlaceHolderMain section of the form, and copy/paste the ScriptLink references referenced in the MSDN article. Save the form, it’ll prompt you that you are breaking from the Site Definition – go ahead, dance with the devil.
(This is just a snippet – you need to grab all the JS from the article)
6. In your browser, navigate to the EditForm
7. Add a Content Editor Web Part, and point it at the JS file you just created.
8. Lastly, add a Script Editor webpart on that same Edit Form, and include just a tiny bit of HTML
9. Rejoice in all that is awesome when you have a People Picker control on your Edit Form page!!
Please remember to SharePoint responsibly!