Signaturen mangler på dokumentet, så det er ikke godkjent.

In Norwegian, the definite article is usually attached to the end of the noun.

• en signatur = a signature
• signaturen = the signature
• et dokument = a document
• dokumentet = the document

So -en and -et are the Norwegian equivalents of the here. The sentence is talking about a specific signature and a specific document, not just any signature or any document.

Mangler is the present tense of å mangle. Here it means is missing or is lacking.

So Signaturen mangler means The signature is missing.

A useful detail: å mangle is different from å savne.

• å mangle = to lack / to be missing
• å savne = to miss someone emotionally

So you would say Jeg savner deg for I miss you, but Dokumentet mangler en signatur for The document lacks a signature.

Yes, both are possible.

• Signaturen mangler på dokumentet focuses on the missing signature.
• Dokumentet mangler en signatur focuses on the document and says it lacks a signature.

There is also a third common option:

• Det mangler en signatur på dokumentet

That is a very natural Norwegian way to say that a signature is missing. Norwegian often allows you to choose different sentence structures depending on what you want to emphasize.

Because a signature is normally placed on a document, so på is the natural preposition.

• på dokumentet = on the document
• i dokumentet = in the document

I dokumentet would sound more like something contained within the text or content of the document. For a physical signature written on the paper or signature line, på dokumentet is the normal choice.

Here så means so or therefore. It connects the first idea to the result:

• the signature is missing
• so the document is not approved

It is introducing a consequence. In this sentence, så works like a coordinating conjunction linking two main clauses.

Because this så is being used as a conjunction between two main clauses. The second clause keeps normal main-clause word order:

• det er ikke godkjent

So after the conjunction, you still get subject + verb.

A useful comparison:

• ..., så det er ikke godkjent = correct here
• ..., derfor er det ikke godkjent = also correct, but with derfor you get inversion

So så here does not behave like derfor.

Det refers to dokumentet.

That matters because dokument is a neuter noun:

• et dokument
• dokumentet
• pronoun: det

If it referred to signaturen, the pronoun would be den, because signatur is a common-gender noun:

• en signatur
• signaturen
• pronoun: den

So the sentence is saying that the document is not approved, not that the signature is not approved.

Godkjent is the past participle of å godkjenne, which means to approve.

So:

• å godkjenne = to approve
• godkjent = approved

In det er ikke godkjent, it functions like approved in English. It can be understood as a past participle and also very much like an adjective describing the document’s status.

Er ikke godkjent describes a state or status: the document is currently not approved.

• det er ikke godkjent = it is not approved
• det blir ikke godkjent = it is not being approved / it will not be approved

So er ikke godkjent is the more natural choice when you mean the document does not have approved status because the signature is missing.

That is normal main-clause word order in Norwegian. In a main clause, ikke usually comes after the finite verb.

So:

• det er ikke godkjent

That is the standard pattern.

Compare it with a subordinate clause:

• fordi det ikke er godkjent

So one very important Norwegian pattern is:

• main clause: verb before ikke
• subordinate clause: ikke before the finite verb

Yes, often you can.

• signatur = signature
• underskrift = signature, often especially a written signature on a document

In many document-related contexts, underskrift may sound slightly more specific and practical, especially for signing forms or official papers. But signatur is also natural and correct here.

For example:

• Underskriften mangler på dokumentet
• Dokumentet mangler underskrift

Both are very natural Norwegian.