Takový doklad potřebuji.

Both are correct.

Czech word order is much more flexible than English word order. The most neutral order would often be:

Potřebuji takový doklad.
= I need such a document / a document like that.

When you say:

Takový doklad potřebuji.

you are putting takový doklad first for emphasis or contrast. It can sound like:

• That kind of document is what I need
• A document like that is what I need

So the sentence you have is not strange; it just highlights the object more strongly.

Takový means such, that kind of, or like that.

In this sentence, it describes doklad, so together takový doklad means:

• such a document
• that kind of document
• a document like that

It is an adjective-like word, so it changes form to match the noun it goes with.

Because it agrees with doklad in:

• gender: masculine inanimate
• number: singular
• case: accusative

The noun doklad is masculine inanimate singular, and in the accusative singular, masculine inanimate nouns usually look the same as in the nominative. The adjective also takes the matching form:

• nominative singular masculine inanimate: takový doklad
• accusative singular masculine inanimate: takový doklad

So here the form happens to look the same as the basic dictionary form.

Because doklad is a masculine inanimate noun.

In Czech, direct objects are usually in the accusative case. But for masculine inanimate nouns, the accusative singular is often identical to the nominative singular.

So:

• nominative: doklad
• accusative: doklad

That is why you do not see a visible change here, even though it is the object of the verb.

Potřebuji is the 1st person singular present tense form of potřebovat (to need).

So it means:

• I need

A useful mini-paradigm:

• potřebuji = I need
• potřebuješ = you need
• potřebuje = he/she/it needs

You may also hear the colloquial form potřebuju, which is very common in spoken Czech. Potřebuji is standard and perfectly correct.

Because Czech often leaves out subject pronouns when they are not needed.

The verb form potřebuji already tells you that the subject is I. So:

• Potřebuji = I need

You could say Já takový doklad potřebuji, but adding já usually gives extra emphasis, something like:

• I need that kind of document

So the version without já is normal and natural.

Not always.

Doklad can mean several related things depending on context, for example:

• document
• proof
• certificate
• ID / identity document
• receipt in some contexts

So the exact English translation depends on the situation. In this sentence, the meaning is something like document or proof/document of that kind.

Because Czech has no articles.

English uses a/an and the, but Czech does not have direct equivalents that must be used in every sentence.

So takový doklad can mean something like:

• such a document
• that kind of document
• sometimes even such document, depending on context

The exact definiteness is understood from the situation rather than from an article.

Yes, but the meaning changes.

• takový doklad = such a document / that kind of document
• tenhle doklad = this document
• tento doklad = this document (more formal/written)

So takový is about the type or kind of document, not about pointing to one specific document in space.

A simple pronunciation guide is:

TA-ko-vee DOK-lat po-TRE-boo-yi

A few useful notes:

• Czech stress is usually on the first syllable of each word.
• ř in potřebuji is a special Czech sound, difficult for English speakers. If you cannot say it yet, that is normal.
• The final d in doklad is often pronounced closer to t at the end of the word, so it may sound a bit like doklat.

A more approximate pronunciation:

TAK-oh-vee DOCK-luht poh-TRZHE-boo-yee

It is basically neutral standard Czech.

• potřebuji is standard and works in both speech and writing.
• The word order with Takový doklad first adds emphasis, but it is still normal Czech.
• In very casual speech, many speakers would say potřebuju instead of potřebuji.

So the sentence is not especially formal, just standard and natural.