В случае если оригинал документа не готов, нужен дубликат.

В случае если means in the event that or if it happens that. It is more formal and bureaucratic than plain если.

• Если оригинал документа не готов, нужен дубликат. = If the original document is not ready, a duplicate is needed.
• В случае если оригинал документа не готов, нужен дубликат. = In the event that the original document is not ready, a duplicate is needed.

So the sentence has a slightly official, document-style tone.

Because the phrase is в случае, and the preposition в here requires the prepositional case.

• случай = nominative
• в случае = prepositional

This is a fixed expression meaning in the case/event of.

So:

• в случае чего-либо = in the case of something
• в случае если... = in the event that...

Документа is in the genitive singular because it depends on оригинал.

Russian often uses this structure where one noun describes another:

• оригинал документа = the original of the document
• копия документа = a copy of the document
• страница книги = a page of the book

So документа answers the question of what?
Оригинал чего? → документа

Yes. Не готов literally means not ready.

Here готов is the short form of the adjective готовый.

• готовый = the full form, used before a noun more like ready/prepared
• готов = the short form, usually used as the predicate, meaning is ready

So:

• документ готов = the document is ready
• документ не готов = the document is not ready

In this sentence, оригинал документа не готов means that the original document has not yet been prepared, completed, or made available.

Because Russian usually uses the short form adjective after the noun when it means something like a current state.

Compare:

• готовый документ = a ready/prepared document
• документ готов = the document is ready

In your sentence, the idea is predicative: it says something about the state of the document. So готов is the natural form.

Since оригинал is masculine singular, the short form is:

• masculine: готов
• feminine: готова
• neuter: готово
• plural: готовы

In the present tense, Russian normally omits the verb to be.

So:

• документ готов literally looks like document ready
• but it means the document is ready

Likewise:

• нужен дубликат literally looks like needed duplicate
• but it means a duplicate is needed

This is one of the most important differences from English: present-tense is/are/am is usually not stated in Russian.

Нужен agrees with дубликат, which is a masculine singular noun.

This pattern means something is needed:

• нужен дубликат = a duplicate is needed
• нужна копия = a copy is needed
• нужно разрешение = permission is needed
• нужны документы = documents are needed

So the form changes according to the noun:

• masculine singular: нужен
• feminine singular: нужна
• neuter singular: нужно
• plural: нужны

Both are possible, but the emphasis changes.

• нужен дубликат sounds like what is needed is a duplicate
• дубликат нужен puts more focus on the duplicate

Russian word order is more flexible than English, and it often reflects emphasis or information structure rather than basic grammar.

In this sentence, нужен дубликат sounds natural and slightly formal, especially in administrative language.

Not exactly.

• копия = copy
• дубликат = duplicate, often an officially issued replacement that has the same legal force as the original

In everyday English, both might sometimes be translated similarly, but in official contexts дубликат often means more than just a photocopy. It can mean a formally recognized replacement for a lost, missing, or unavailable original.

So in a bureaucratic sentence like this, дубликат is a very appropriate word.

Because В случае если оригинал документа не готов is a subordinate clause, and it comes before the main clause.

Structure:

• subordinate clause: В случае если оригинал документа не готов
• main clause: нужен дубликат

Russian uses a comma to separate them:

В случае если оригинал документа не готов, нужен дубликат.

This is similar to English punctuation in a sentence like:

If the original document is not ready, a duplicate is needed.

It sounds formal and administrative. That is mostly because of:

• В случае если instead of simple если
• дубликат instead of a more everyday word like копия
• the overall compact, official style

A more everyday version might be:

Если оригинал документа не готов, нужен дубликат.

That keeps the same meaning but sounds less bureaucratic.