Izvadak mora biti čitljiv.

Izvadak is the nominative singular form, because it is the subject of the sentence.

In Izvadak mora biti čitljiv, the thing that must be legible is izvadak, so Croatian uses the basic dictionary form here.

A native English speaker may notice there is no article. Croatian normally does not use words like the or a/an, so izvadak can mean the extract/document/excerpt depending on context.

Mora is the 3rd person singular present tense of the verb morati, which means to have to / must.

So:

• ja moram = I must
• ti moraš = you must
• on/ona/ono mora = he/she/it must

Since izvadak is grammatically singular, the verb is also singular: mora.

After the modal verb morati, Croatian normally uses the infinitive of the main verb.

So:

• mora biti = must be
• mora doći = must come
• mora stati = must stop

This is very similar to English:

• must be
• must come

So biti stays in the infinitive because it depends on the modal verb mora.

Čitljiv is an adjective, and it agrees with izvadak in gender and number.

Since izvadak is:

• masculine
• singular

the adjective must also be masculine singular:

• čitljiv = masculine singular
• čitljiva = feminine singular
• čitljivo = neuter singular

For example:

• Knjiga mora biti čitljiva. = The book must be legible/readable.
• Pismo mora biti čitljivo. = The letter must be legible/readable.

Yes. In this sentence, čitljiv is a predicate adjective after biti, so it matches the subject izvadak.

That is why it appears in the same basic agreement form: masculine singular nominative.

This is similar to other Croatian sentences with biti:

• On je umoran.
• Dokument je važan.
• Izvadak mora biti čitljiv.

Čitljiv means legible or readable, especially in the sense that something can be read clearly.

It is often used in formal or administrative language, for example about:

• handwriting
• printed text
• forms
• copies of documents

So in this sentence it suggests that the extract/document must be clear enough to read.

Yes, although they are often close in meaning.

• čitljiv = readable, legible
• čitak = clear to read, often very neat or visually clear

In many contexts they overlap, but čitljiv is especially common in formal instructions and document-related language.
So Izvadak mora biti čitljiv sounds natural in an official or administrative setting.

Yes, Croatian word order is fairly flexible, but Izvadak mora biti čitljiv is the most neutral and natural order.

You may also see different word orders for emphasis, for example:

• Čitljiv mora biti izvadak.
• Izvadak čitljiv mora biti.

These are much more marked and would usually sound unusual without a specific context. For a learner, the safest choice is the standard order:

• subject + modal verb + infinitive + adjective

So: Izvadak mora biti čitljiv.

Croatian does not have articles like English a/an and the.

So izvadak can mean:

• an extract
• the extract
• the document extract

Which one is intended depends on context.

That is very normal in Croatian, and learners need to get used to understanding definiteness from the situation rather than from an article.

A rough pronunciation guide is:

• či- like chi in chip, but with a firmer ch sound
• -tljiv has a consonant cluster that may feel difficult at first

A rough English-style approximation is something like CHEET-lyiv, though not perfectly.

Two sounds that often matter here are:

• č = like ch in church
• lj = a soft sound, somewhat like lli in million for many learners

You do not need to pronounce it exactly like English spelling suggests. The important thing is to notice that č and lj are separate Croatian sounds.

Yes, it sounds fairly formal and would fit well in:

• administrative instructions
• official forms
• document requirements
• legal or bureaucratic language

That is because words like izvadak and čitljiv are common in official contexts. In everyday speech, people might choose a different noun depending on what the document actually is, but the grammar would stay the same.

In this sentence, biti should stay.

With morati, if you want to say must be, Croatian normally uses:

• mora biti

So:

• Izvadak mora biti čitljiv. = correct

Leaving out biti would not work here, because čitljiv is describing a state, and Croatian needs the verb biti with the modal to express that properly.