O valor total aparece no documento.

Because valor is a singular masculine noun, and in normal Portuguese you usually need an article or some other determiner before it.

• o = the for masculine singular nouns
• valor = a masculine singular noun

So:

• o valor total = the total amount / the total value

If you removed o and said Valor total aparece no documento, it would sound incomplete in a normal sentence, although article-less phrases can appear in titles, headings, forms, or labels.

In Portuguese, adjectives often come after the noun, much more often than in English.

So:

• valor total = literally value total
• natural English = total value or total amount

Putting total after the noun is the normal order here.
Sometimes Portuguese adjectives can go before the noun, but that often changes the tone or meaning. In this case, valor total is the standard, neutral expression.

Valor can mean several related things, depending on context:

• value
• amount
• sum
• sometimes even worth

In a sentence like O valor total aparece no documento, it often means the total amount or the total value, especially in billing, financial, or administrative contexts.

So although the dictionary meaning is often value, the best English translation may be amount if the document is showing money.

Aparece is from the verb aparecer, which usually means:

• to appear
• to show up
• to be shown
• to be visible

In this sentence, aparece no documento means something like:

• appears in the document
• shows up on the document
• is shown in the document

It is in the 3rd person singular present because the subject is o valor total.

• eu apareço = I appear
• tu apareces = you appear
• ele/ela/você aparece = he/she/you appears

Because the subject is singular:

• o valor total = singular

So the verb must also be singular:

• O valor total aparece...

If the subject were plural, the verb would change:

• Os valores totais aparecem no documento.
  = The total amounts appear in the document.

This is basic subject-verb agreement in Portuguese.

Because no is the contraction of:

• em + o = no

So:

• no documento = in the document / on the document, depending on context

Portuguese very often contracts prepositions with articles:

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

So em o documento is not the normal form; no documento is.

It can correspond to either in English, depending on context.

Portuguese uses em very broadly, where English might choose either in or on.

So:

• no documento can mean in the document
• or on the document

If it is a written form, bill, certificate, or official paper, English often prefers on the document or in the document, depending on how natural it sounds in context.

So the Portuguese structure is straightforward, even if English has two possible prepositions.

Yes, and it is similar, but not exactly the same.

• aparece no documento suggests that the total amount appears / is shown / is visible in the document.
• está no documento simply means it is in the document.

So aparece focuses a bit more on the idea of showing up or being displayed, while está is more neutral and simply locates it.

In many real situations, both could work, but aparece is slightly more specific.

Yes. Aparece is the present indicative form of aparecer.

So the sentence is in the present tense:

• O valor total aparece no documento.

Depending on context, the present can be translated in English as:

• The total amount appears on the document.
• The total amount is shown on the document.

Portuguese often uses the simple present in places where English might prefer a passive structure like is shown.

In European Portuguese, unstressed vowels are often reduced, so the sentence may sound less like the spelling than an English speaker expects.

A rough approximation is:

• O valor total aparece no documento
• roughly: u vuh-LOR tuh-TAL uh-puh-REH-s(uh) nuh duh-kuh-MEN-tu

A few useful notes for Portugal Portuguese:

• o at the beginning often sounds close to u
• unstressed a/e/o are often reduced
• final e in aparece is often very weak
• de / do / no can sound quite reduced in fast speech

This reduction is one of the big differences between European Portuguese and Brazilian Portuguese.

Sometimes yes, but it changes the feel.

Portuguese often allows subject omission because the verb ending gives information about the subject. However, in this case:

• Aparece no documento = It appears in/on the document or Appears in/on the document

That can work only if the subject is already understood from context.
If you want a complete, clear standalone sentence, O valor total aparece no documento is better.

So:

• with context: Aparece no documento.
• as a full sentence: O valor total aparece no documento.

You need to change the article, noun, adjective, verb, and the contracted preposition if necessary.

Singular:

• O valor total aparece no documento.

Plural:

• Os valores totais aparecem nos documentos.

Changes:

• o → os
• valor → valores
• total → totais
• aparece → aparecem
• no → nos
• documento → documentos

This is a good example of how several words in Portuguese must agree in number.