Elements from adobe web form are under elements from the PDF

Ok!, first I add a checkbox inside the black square that is already in the pdf manually or from the API it doesn't matter and when you open then after editing the pdf you will can see the checkbox, any problem here

Then if I select the property read only to that checkbox manually or from the API 

When you open the pdf without editing it just dissapear from the pdf but what is happening is that is under the black square

Thats why if I select that checkbox from default it will be a read only black circle under the black square

is like the white space inside the black border square isn't transparent, and it seems the read only element (it doesn't matter the element, goes under things