Add webpart to SharePoint default NewForm.aspx, EditForm.aspx or DisplayForm.aspx

This is simple trick to add OOTB webpart or custom webpart to SharePoint default form.aspx in your SharePoint List or Document Library.

Pass below url parameters after .aspx

?PageView=Shared&ToolPaneView=2

This will change the page in edit mode where you could see the webpart zone to add other webpart.
Once you’ve completed your update, just save the page.
Then you will have the option to edit the page from Site Actions later on.