Я лично проверил документ.

A natural pronunciation is:

Я ли́чно прове́рил докуме́нт.

Stress falls on:

• ли́чно
• прове́рил
• докуме́нт

A rough English-style approximation is:

ya LEECH-na pra-VYE-ril da-ku-MYENT

That said, Russian pronunciation does not match English exactly, so this is only a guide.

Проверил is past tense.

It comes from the infinitive проверить (to check / to verify). In the past tense, Russian often adds -л to the verb stem:

• проверить → проверил for a masculine speaker

So the sentence describes a completed action in the past: I checked / verified the document.

Yes. In the Russian past tense, the verb agrees with the subject in gender and number.

Here:

• проверил = masculine singular
• проверила = feminine singular
• проверило = neuter singular
• проверили = plural

So if a woman says this sentence, she would normally say:

Я лично проверила документ.

This is an aspect question.

• проверил is perfective
• проверял is imperfective

In this sentence, проверил suggests a completed, finished check: the document was checked successfully as a whole.

By contrast, проверял would usually mean something like:

• was checking
• used to check
• checked with focus on process rather than result

So:

• Я лично проверил документ. = I personally checked the document. / I personally verified it.
• Я лично проверял документ. = I was personally checking the document / I personally checked it (process-focused, less emphasis on completion).

Лично means personally.

It adds emphasis: the speaker is saying that they themselves took part in the checking, not just indirectly or through someone else.

Compare:

• Я проверил документ. = I checked the document.
• Я лично проверил документ. = I personally checked the document.

So лично adds a sense of personal involvement or responsibility.

Yes, but the nuance is a little different.

• лично = personally
• сам = myself / by myself

Compare:

• Я лично проверил документ. = I personally checked the document.
• Я сам проверил документ. = I checked the document myself.

Сам often stresses that I did it, not someone else.
Лично often stresses personal involvement or personal responsibility.

In many contexts they are close, but they are not always identical.

Документ is the direct object of проверил, so it is in the accusative case.

However, for inanimate masculine singular nouns, the accusative form is usually the same as the nominative form.

So:

• nominative: документ
• accusative: документ

That is why the form does not change.

A useful comparison:

• Я вижу стол. = I see the table.
• Я вижу брата. = I see my brother.

Here стол is inanimate, so accusative looks like nominative.
But брат is animate, so accusative changes.

Я is in the nominative case because it is the subject of the sentence.

It is the person performing the action:

• Я = I
• проверил = checked
• документ = document

So the structure is basically:

subject + adverb + verb + object

Sometimes Russian does omit subject pronouns, but here я is usually helpful.

Why? Because the past tense form проверил tells you:

• singular
• masculine

But it does not by itself tell you whether the subject is I or he.

So without context, проверил could refer to I or he.

That means:

• Я лично проверил документ. is clear on its own.
• Лично проверил документ. would usually need prior context.

So unlike some present-tense forms, the pronoun is often more important in the past tense.

Russian word order is flexible, and the order can change for emphasis.

The original sentence is a normal, natural order:

Я лично проверил документ.

Other possible versions include:

• Лично я проверил документ.
  This emphasizes I personally.
• Документ я лично проверил.
  This emphasizes the document.
• Я проверил документ лично.
  Possible, but less neutral in many contexts.

So the original version is a very natural neutral choice, but Russian allows movement of words to highlight different parts of the message.

Russian has no articles like English a/an or the.

So документ can mean:

• a document
• the document

The exact meaning depends on context.

In many real situations, this sentence would be translated as I personally checked the document, because both speaker and listener already know which document is meant. But Russian itself does not use an article to mark that.