Jag öppnade dokumentet, men bilagan var inte där.

Öppnade is the past tense (preterite) of öppna, meaning to open.

• öppna = to open
• öppnade = opened

So Jag öppnade dokumentet means I opened the document.

Because öppnade is the simple past form used on its own:

• Jag öppnade dokumentet = I opened the document

Öppnat is the supine form, which is used with har to make the present perfect:

• Jag har öppnat dokumentet = I have opened the document

So:

• öppnade = simple past
• har öppnat = present perfect

Because dokumentet is the definite singular form: the document.

The base word is:

• ett dokument = a document

Since dokument is an ett-word (neuter gender), the definite ending is -et:

• dokument = document
• dokumentet = the document

Because bilagan is also in the definite singular: the attachment or the appendix, depending on context.

The base word is:

• en bilaga = an attachment / an appendix

Since bilaga is an en-word (common gender), its definite singular form is:

• bilagan = the attachment

So the sentence uses two definite nouns:

• dokumentet = the document
• bilagan = the attachment

Bilaga usually means attachment, enclosure, or appendix, depending on context.

In this sentence, bilagan most naturally means:

• an attached file
• an attachment to a document or email
• possibly an appendix to a document

So the exact English translation can vary a little depending on the situation.

In a Swedish main clause, the finite verb usually comes in the second position. This is often called the V2 rule.

Here:

• bilagan = subject
• var = finite verb
• inte = not
• där = there

So the normal order is:

• Bilagan var inte där.

This is the usual Swedish pattern in main clauses:
subject + verb + inte + ...

Compare:

• Jag kommer inte. = I am not coming.
• Han såg inte bilen. = He did not see the car.

Yes. In many subordinate clauses, inte comes before the verb.

Compare:

• Bilagan var inte där. = The attachment was not there.
  (main clause)

• ... att bilagan inte var där. = ... that the attachment was not there.
  (subordinate clause)

So this is an important contrast:

• main clause: verb before inte
• subordinate clause: inte before verb

Där means there.

So:

• var inte där = was not there

It refers to location or presence in a place, either literally or more abstractly, like in a document, file, folder, or email.

Yes, sometimes. Both can work, but they are slightly different in feel.

• var inte där = was not there
• fanns inte där = was not there / did not exist there / could not be found there

In many everyday situations, both are possible.
But var inte där is very natural when you simply mean that something was missing from the place where you expected it.

Not always. In Swedish, commas are often used more lightly than in English.

You may see both:

• Jag öppnade dokumentet, men bilagan var inte där.
• Jag öppnade dokumentet men bilagan var inte där.

Both are acceptable in many contexts. The comma can help readability, but it is not as strictly required as in some English writing styles.

Very close to the written version. In speech, a speaker might slightly emphasize inte or där if they are expressing surprise or annoyance:

• Jag öppnade dokumentet, men bilagan var inte där.

This is already a natural everyday sentence. Swedish usually does not need extra words like actually or just here unless the speaker wants added emphasis.