Some tax forms like NY State fill-in forms have some scripted functionality that requires Adobe Acrobat to work, and they block rendering from other PDF programs. Even worse, once you've filled in the form, their PDF then blocks Acrobat from exporting to a normal PDF (the way you can save a print preview to a PDF for later) and so the only way you can get a real PDF of it is to print it directly and then scan it back to your computer.