A cópia autenticada está com o documento original.

In Brazilian Portuguese, cópia autenticada usually means a certified copy or notarized copy in an administrative/legal sense.

It is not just any copy that happens to be accurate. It normally refers to a copy that was officially checked against the original and stamped or certified, often at a cartório in Brazil.

So even though autenticada literally looks like authenticated, in real-life Brazilian usage the best English translation may be certified copy depending on the context.

Because cópia is a feminine singular noun.

That means the article and adjective must agree with it:

• a = feminine singular the
• autenticada = feminine singular form of authenticated/certified

So:

• a cópia autenticada = the certified copy

If the noun were masculine, the forms would change:

• o documento autenticado = the certified document

This is standard gender and number agreement in Portuguese.

For the same reason: adjective agreement.

Autenticada is agreeing with cópia, which is feminine:

• cópia → feminine
• autenticada → feminine form

Compare:

• a cópia autenticada
• o documento autenticado

The ending changes to match the noun.

Because estar is used here for a temporary state, location, or situation.

In this sentence, está com means something like:

• is with
• is together with
• is accompanied by

That is the kind of idea Portuguese normally expresses with estar, not ser.

So:

• A cópia autenticada está com o documento original = the certified copy is with / together with the original document

Using é com here would sound wrong.

Literally, com means with, but estar com is a very common Portuguese pattern with a few related meanings.

Here, it most likely means:

• is with
• is together with
• is accompanied by

In other contexts, estar com can also mean to have something in your possession:

• Ela está com o passaporte. = She has the passport with her.

So in this sentence, the idea is probably that the certified copy is together with the original document, not separated from it.

Yes.

Portuguese often puts the adjective after the noun, so:

• documento original = original document

This is very normal word order in Portuguese.

English usually says:

• adjective + noun → original document

Portuguese often says:

• noun + adjective → documento original

So the phrase is completely natural.

Because the sentence is talking about specific items:

• a cópia autenticada = the specific certified copy
• o documento original = the specific original document

Portuguese uses definite articles very often, often more than English does.

In a note, label, or list, articles might sometimes be dropped, but in a full normal sentence they are very natural here.

Normally, no.

The most natural order here is:

• cópia autenticada
• documento original

Portuguese often places descriptive adjectives after the noun, especially in formal or administrative language.

Putting them before the noun here would sound unnatural, overly literary, or simply wrong in normal usage.

Not necessarily.

Está com does not automatically mean they are physically stapled or attached. It more generally means they are together, accompanying each other, or in the same set/context.

Depending on the situation, it could mean:

• the copy was submitted together with the original
• the copy is in the same folder as the original
• the copy comes along with the original for verification

If you specifically wanted to say attached, Portuguese might use something more explicit, such as:

• anexada ao documento original
• presa ao documento original

It is understandable and natural enough, especially in bureaucratic or administrative contexts, but the exact best wording depends on what you want to emphasize.

Other common possibilities include:

• A cópia autenticada está junto com o documento original.
• A cópia autenticada veio acompanhada do documento original.
• A cópia autenticada foi apresentada com o documento original.

Your sentence is fine, but está com can sound a little broad, because it can mean simple accompaniment rather than a very precise legal relationship.

Yes, a little.

Because estar com can mean to be with or to have, the sentence may feel slightly open to interpretation without context.

A listener will probably understand that the certified copy is together with the original document, but if you want to be more precise, you could choose a clearer phrasing.

For example:

• A cópia autenticada está junto com o documento original.
• A cópia autenticada acompanha o documento original.
• A cópia autenticada foi apresentada junto com o documento original.

These reduce ambiguity.

It comes from the verb autenticar, which means to authenticate, to certify, or to notarize depending on context.

Its participle is:

• autenticado = masculine
• autenticada = feminine

In this sentence, that participle is being used like an adjective:

• cópia autenticada = authenticated/certified copy

So grammatically, it works the same way as many other Portuguese past participles used adjectivally.