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

Because prestes a is used with estar, not ser.

• estar prestes a + infinitive = to be about to + verb
• So Estou prestes a imprimir means I’m about to print

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

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

So:

• Estou prestes a imprimir = I’m about to print
• It suggests the action will happen very soon, maybe immediately.

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

Because the expression is estar prestes a + infinitive.

That a is required by the expression. It links prestes to the verb that follows.

Examples:

• Estou prestes a sair. = I’m about to leave.
• Ela está prestes a começar. = She is about to begin.

So in your sentence:

• estou prestes a imprimir = I’m about to print

Because after prestes a, Portuguese uses the infinitive form of the verb.

So:

• estou prestes a imprimir
• not estou prestes a imprimo
• not estou prestes a imprimindo

This is similar to English about to print, where the second verb also stays in a base form.

Portuguese often uses definite articles more frequently than English.

Here, a última página literally means the last page:

• a = the
• última = last
• página = page

In many cases, Portuguese sounds more natural with the article where English might or might not use one.

Because última agrees with página, and página is feminine.

In Portuguese, adjectives usually agree in gender and number with the noun:

• o último capítulo = the last chapter
• a última página = the last page

So:

• página = feminine singular
• última = feminine singular

Because mas means but, and it connects two contrasting ideas.

The sentence has two parts:

• Estou prestes a imprimir a última página
• mas quero revisar a pontuação mais uma vez

The comma helps separate those clauses, just as in English:

• I’m about to print the last page, but I want to review the punctuation one more time.

In standard writing, a comma before mas is normal.

This is a very common confusion.

• mas = but
• mais = more

In the sentence:

• mas quero revisar... = but I want to review...
• mais uma vez = one more time

So even though they look similar, they have completely different meanings.

A quick memory trick:

• mas = contrast
• mais = quantity or addition

After querer, Portuguese normally uses the infinitive.

So:

• quero revisar = I want to review
• quero imprimir = I want to print
• quero sair = I want to leave

Using revisando here would be incorrect.

Usually, yes. Revisar means to review, to check, or to revise, depending on context.

In this sentence, it means something like:

• check over
• review carefully
• go through again

So quero revisar a pontuação means I want to review/check the punctuation.

Again, Portuguese often uses articles where English may not.

• revisar a pontuação = review the punctuation

Even though English might sometimes just say review punctuation, Portuguese strongly prefers a pontuação here.

Also, pontuação can refer specifically to the punctuation in the text you are working on, so the definite article sounds natural.

Not always. Pontuação can mean:

• punctuation in writing
• score/points in other contexts

Examples:

• A pontuação do texto está errada. = The punctuation of the text is wrong.
• A pontuação do time melhorou. = The team’s score improved.

In your sentence, because it is about printing and reviewing a page, pontuação clearly means punctuation.

Mais uma vez means one more time or once again.

Breakdown:

• mais = more
• uma vez = one time / once

So:

• revisar a pontuação mais uma vez = review the punctuation one more time

It suggests repeating the action again before printing.

Yes, often you could.

• mais uma vez = one more time / once again
• de novo = again

So:

• quero revisar a pontuação mais uma vez
• quero revisar a pontuação de novo

Both are natural, but there is a small nuance:

• mais uma vez emphasizes one additional time
• de novo simply means again

In this sentence, mais uma vez fits very well because the speaker wants to do one last extra check.

Because estar prestes a + infinitive is a present-tense structure that expresses an immediate future.

This is very similar to English:

• I am about to print
• not I will about to print

So Portuguese uses estou in the present, but the meaning points to something that is going to happen very soon.

Yes, there is a nuance.

• Vou imprimir = I’m going to print
• Estou prestes a imprimir = I’m about to print

Vou imprimir is a general near future. Estou prestes a imprimir is more immediate and specific: the action is just about to happen.

So in your sentence, estou prestes a imprimir suggests the person is right at the final step before printing.

Yes. Portuguese allows some flexibility.

For example:

• Quero revisar a pontuação mais uma vez.
• Quero revisar mais uma vez a pontuação.

Both are understandable and natural.

The original version is especially smooth because a pontuação stays right after revisar, and mais uma vez comes at the end as a time/frequency expression.

A few useful pronunciation notes for Brazilian Portuguese:

• última: 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

A rough English-style approximation:

• última ≈ OOL-chee-ma or OOL-ti-ma depending on accent
• página ≈ PAH-zhee-na or PAH-jee-na
• pontuação ≈ pon-too-a-SOWN

These are only approximations, but they help you notice the stressed syllables and the nasal sound in -ção.

Yes, it sounds natural and well-written.

It has a slightly careful, polished tone because of expressions like:

• estou prestes a
• revisar
• mais uma vez

A Brazilian speaker could absolutely say this, especially in a context involving writing, editing, or printing a document.