Is there a way to move the paid stamp so that it is not in the center of the page and covering line items from view?

Yes there is!  It has taken me years and finally I can place it at the right side under the Payment  or Balance Due.  This is what I did.  Go to Gear symbol on the top right of the page.  Click on it and select

"Custom Form Styles".  Once  you are in this section look for : Name - Standard. Form Type: Master.  If you can make it the default under the down arrow on the right side then do that.  I could not.  So what I did was delete the other two invoice templates that I had forcing the Standard Master template to be the default.  Then click on edit beside the Master template.  Then click on Design.  Then : Change up the template.  Select: Airy New.  This one will give you the paid stamp in the correct place.   Good luck!  I'm pretty happy it works for me now.