Need help writing text on a basic shape

I have a PDF document of a floor plan from a client.  I am trying to add basic shapes like squares, circles, and diamonds to it to indicate where a sample should be collected.  I want to type a unique identification directly on that shape.  It seems like I cant do that without adding a text box to the shape.  That is super labor intensive and then I can't lock the shape and the text together to position it on the document correctly.

Please help, my due date for this project is very soon. I've been struggling with this for a week.