Dokumentet er færdigt, bortset fra at pupilafstanden mangler.

Dokumentet means the document.

In Danish, the definite article is usually added to the end of the noun instead of being a separate word like English the.

• et dokument = a document
• dokumentet = the document

Because the sentence is talking about a specific document, Danish uses dokumentet.

The -t is there because dokumentet is a neuter noun.

The adjective færdig must agree with the noun it describes:

• en rapport er færdig
• et dokument er færdigt

So:

• Dokumentet er færdigt = The document is finished / ready

This is a very common pattern in Danish: after er, adjectives still agree with the gender and number of the noun.

Here færdigt means finished, complete, or ready.

In this sentence, it suggests that the document is basically complete, except for one missing piece.

Depending on context, færdig can mean:

• finished
• done
• ready

So Dokumentet er færdigt could be understood as The document is complete or The document is ready.

Bortset fra means except for or apart from.

Examples:

• Alt er klart, bortset fra døren.
  Everything is ready except the door.
• Jeg forstod alt, bortset fra det sidste.
  I understood everything except the last part.

In your sentence, it introduces the exception to the statement that the document is finished.

Because what follows is a clause, not just a noun phrase.

Compare:

• bortset fra navnet = except for the name
  Here, navnet is a noun.

• bortset fra at navnet mangler = except that the name is missing
  Here, navnet mangler is a full clause.

In your sentence:

• bortset fra at pupilafstanden mangler

This means except that the pupil distance is missing.

So at is used because a whole statement follows.

Mangler means is missing or is lacking.

It comes from the verb at mangle.

Examples:

• Jeg mangler penge.
  I lack money.
• Der mangler en side.
  A page is missing.
• Pupilafstanden mangler.
  The pupil distance is missing.

In this sentence, it means that this piece of information has not been filled in or included.

Because after at, Danish usually uses normal subordinate clause word order.

The clause is:

• at pupilafstanden mangler

This is simply:

• subject: pupilafstanden
• verb: mangler

That is normal Danish word order for a subordinate clause when there is no adverb changing the position.

A useful thing to know is that Danish main clauses and subordinate clauses often differ in word order, especially when adverbs are involved. But in this example, the clause is straightforward, so it looks similar to English.

Pupilafstanden means the pupil distance.

It is a compound noun:

• pupil = pupil
• afstand = distance
• pupilafstand = pupil distance
• pupilafstanden = the pupil distance

This is the distance between the pupils of the eyes, often used for glasses or optical documents.

Danish forms many nouns by combining smaller nouns into one word, so long compounds like this are very common.

Because Danish, like German, very often writes compound nouns as a single word.

So instead of writing something like pupil distance as two words, Danish combines them:

• pupil
  • afstand = pupilafstand

Then the definite ending is added:

• pupilafstanden = the pupil distance

This is completely normal in Danish and something English speakers need to get used to.

Yes. Depending on context, færdigt can mean:

• finished
• complete
• ready

In this sentence, The document is finished and The document is ready are both possible, but because the second half says something is still missing, The document is complete, except... or The document is finished, apart from... may fit best.

Yes, a few close alternatives are possible, for example:

• Dokumentet er færdigt, bortset fra pupilafstanden.
• Dokumentet er færdigt, men pupilafstanden mangler.
• Dokumentet er næsten færdigt; pupilafstanden mangler stadig.

Your original sentence is completely natural, but these alternatives may sound slightly simpler or more direct depending on context.

Yes, it sounds fairly neutral to formal, especially because of words like dokumentet and pupilafstanden.

It would fit well in contexts such as:

• administration
• healthcare
• opticians
• official communication
• written notes

It is not overly stiff, but it definitely sounds more like practical written Danish than casual conversation.