Learn Hardcore Portuguese (Brazil): Estou prestes a imprimir a última página, mas quero revisar a pontuação mais uma vez. - I am about to print the last page, but I want to review the punctuation one more time.

última: <a class="border-b border-dotted border-blue-400 dark:border-blue-500 cursor-pointer text-inherit no-underline" href="/grammar/portuguese-brazil/pronunciation/stress-patterns">stress on ÚL
página: stress on PÁ
pontuação: stress near the end, and -ção sounds roughly like sown with a nasal ending in Brazilian Portuguese

Breakdown of Estou prestes a imprimir a última página, mas quero revisar a pontuação mais uma vez.

Why is it estou prestes a and not sou prestes a?

Because prestes a is used with estar, not ser.

This is a fixed expression in Portuguese. Using ser here would sound wrong.

What exactly does prestes a mean?

Prestes a means on the verge of, just about to, or more naturally in English, about to.

So:

It is a bit more formal or polished than simply saying vou imprimir.

Why is there an a before imprimir in prestes a imprimir?