Bitte klicken Sie den Link in der E-Mail an, dann öffnet sich das Dokument.

Because Sie here means the formal you. In German, the formal pronoun Sie is always capitalized, no matter where it appears in the sentence.

Compare:

• Klicken Sie den Link an. = formal, polite
• Klick den Link an. = informal, to one person
• Klickt den Link an. = informal, to several people

So this sentence is written in a polite, formal style, which is very common in instructions and customer-facing messages.

Because the verb is anklicken, which means to click on.

Anklicken is a separable verb:

• dictionary form: anklicken
• in a main clause: Sie klicken den Link an.

So the prefix an- moves to the end of the clause.

That is why you get:

• Bitte klicken Sie den Link in der E-Mail an.

and not:

• Bitte klicken Sie den Link in der E-Mail anklicken.

Because anklicken is a separable verb, and in a normal main clause the prefix goes to the end.

Pattern:

• Ich rufe dich an.
• Wir machen das Fenster auf.
• Bitte klicken Sie den Link an.

So an belongs to klicken, even though it is separated from it.

Because den Link is the direct object of anklicken, so it has to be in the accusative case.

Link is a masculine noun:

• nominative: der Link
• accusative: den Link

So:

• Der Link ist neu. → subject
• Ich klicke den Link an. → direct object

That is why the sentence uses den Link.

There are two things happening here:

1. E-Mail is a feminine noun, so its basic article is die.
2. After in, German uses different cases depending on meaning.

Here, in der E-Mail describes a location: the link is in the email. For location, in takes the dative.

So:

• nominative: die E-Mail
• dative: der E-Mail

That gives:

• in der E-Mail

If it were about movement into something, you would expect the accusative instead.

Yes. In fact, auf den Link klicken is extremely common and often sounds a bit more natural in everyday German.

Both are possible:

• den Link anklicken
• auf den Link klicken

They are very close in meaning. Very roughly:

• anklicken treats the link as a direct object
• auf ... klicken uses a prepositional phrase, more like English click on ...

So a learner will often see both:

• Bitte klicken Sie den Link an.
• Bitte klicken Sie auf den Link.

Because the sentence contains two main clauses:

1. Bitte klicken Sie den Link in der E-Mail an
2. dann öffnet sich das Dokument

Here dann is not a conjunction like und or weil. It is an adverb meaning something like then or after that. Since these are separate main clauses, German uses a comma here.

You could also write them as two sentences:

• Bitte klicken Sie den Link in der E-Mail an. Dann öffnet sich das Dokument.

That would also be correct.

Because German main clauses normally follow the verb-second rule.

Here, dann takes the first position in the clause, so the conjugated verb must come next:

• Dann öffnet sich das Dokument.

Structure:

• position 1: dann
• position 2: öffnet
• then: sich das Dokument

If there were no dann, you could say:

• Das Dokument öffnet sich.

But once dann is moved to the front, the verb stays in second position.

Because German often uses sich öffnen to mean to open in the sense of becoming open.

So:

• Das Dokument öffnet sich. = the document opens

This is a common German way of expressing that something opens by itself or as a result of an action, without naming an outside agent.

Compare:

• Ich öffne das Dokument. = I open the document
• Das Dokument öffnet sich. = the document opens

In English, we often just say the document opens, but in German the reflexive form sich öffnen is very natural here.

Because Dokument is a neuter noun, so its nominative article is das.

In the second clause, das Dokument is the subject, so it stays in the nominative:

• das Dokument

If it were a direct object, you would also get das Dokument, because neuter nominative and accusative look the same. But here it is the subject of öffnet sich.

Yes. It is a formal imperative.

The formal imperative in German uses:

• Verb + Sie

So:

• Klicken Sie!
• Warten Sie!
• Lesen Sie die E-Mail!

Adding bitte makes it more polite:

• Bitte klicken Sie den Link an.

This is the standard style for polite instructions, notices, and customer support messages.

Yes. Bitte is quite flexible.

All of these are possible:

• Bitte klicken Sie den Link an.
• Klicken Sie bitte den Link an.
• Klicken Sie den Link bitte an.

The first version is especially common in written instructions. The meaning stays basically the same, though the rhythm and emphasis can change slightly.

Yes. Here are some very natural alternatives:

• Bitte klicken Sie auf den Link in der E-Mail. Dann öffnet sich das Dokument.
• Klicken Sie bitte auf den Link in der E-Mail, dann öffnet sich das Dokument.
• Wenn Sie auf den Link in der E-Mail klicken, öffnet sich das Dokument.

These are all normal German. The original sentence is clear and idiomatic, especially in an instructional context.