A professora pediu uma margem grande na folha.

A is the feminine singular definite article, meaning the.

• a professora = the teacher
• professora by itself = teacher in a more general or less specified sense

In Portuguese, articles are used more often than in English, so a professora sounds very natural when referring to a specific teacher.

Portuguese nouns for people often change form to match gender.

• professor = male teacher
• professora = female teacher

Because the sentence refers to a female teacher, professora is used.

Pediu is the preterite form of pedir and means asked or requested in a completed past action.

Conjugation here:

• eu pedi = I asked
• você/ele/ela pediu = you/he/she asked

So A professora pediu... means the teacher made that request at a specific moment in the past.

In Portuguese, pedir usually takes a direct object when you ask for a thing.

• pedir algo = to ask for something
• pedir ajuda = to ask for help
• pedir silêncio = to ask for silence

So:

• pediu uma margem grande = asked for a large margin

English often uses ask for, but Portuguese does not need an equivalent of for here.

Uma is the indefinite article, meaning a/an.

• uma margem = a margin
• a margem = the margin

Using uma suggests the teacher requested a large margin, without identifying a previously known specific one.

In Portuguese, adjectives often come after the noun.

• uma margem grande = a large margin
• um livro interessante = an interesting book

That is the normal word order. Some adjectives can go before the noun, but after the noun is very common and often the most neutral choice.

Yes, uma grande margem is grammatically possible, but it can sound a little different.

• uma margem grande usually emphasizes the physical size more directly
• uma grande margem can sound slightly more subjective or stylistic

In this sentence, uma margem grande is the most straightforward way to talk about the size of the margin on the paper.

Na is a contraction of em + a.

• em = in/on
• a = the
• na = in/on the

So:

• na folha = on the sheet or on the page

This kind of contraction is extremely common in Portuguese:

• no = em + o
• na = em + a
• nos = em + os
• nas = em + as

Yes, folha can mean both leaf and sheet, depending on context.

In this sentence, because it talks about a margin, folha means a sheet of paper.

This is very common:

• folha de papel = sheet of paper
• folha da árvore = leaf of a tree

The context tells you which meaning is intended.

Both can be possible, but they focus slightly differently.

• na folha emphasizes the sheet/page
• no papel emphasizes the paper material or can sound a bit broader

When talking about leaving margins for writing, na folha sounds very natural because it refers to the sheet itself.

No. Margem has several meanings, just like margin in English.

It can mean:

• the edge space on a page
• the bank of a river
• a figurative margin, like room for error or profit margin

In this sentence, the context clearly shows it means the blank space at the edge of the sheet.

Yes, it is natural and correct.

A Brazilian speaker might also say things like:

• A professora pediu uma margem maior na folha.
• A professora pediu para deixar uma margem grande na folha.

But A professora pediu uma margem grande na folha is perfectly understandable and natural.