You might try the manual to the
eforms is another interface (other than
hyperref) for creating PDF forms in TeX. The manual includes many simple examples.
There is no DOM in PDF. If you want parts of the PDF to change based on form events, you pretty much have to make those changing things read-only text fields.
Both of the docs (and the packages they document) are written by D.P. Story, who is extremely prolific in this area. His
acrotex bundle has many more examples.