Saya membaca petunjuk itu.

Baca is the root word, meaning read.
Membaca is the more standard active verb form built from that root.

In Indonesian, many active verbs take the meN- prefix. With baca, that becomes mem-, so:

• baca = read (root)
• membaca = to read / read

In a full, normal sentence, membaca sounds more grammatical and natural, especially in standard Indonesian.

You may hear Saya baca petunjuk itu in casual speech, but Saya membaca petunjuk itu is the more formal or textbook form.

The mem- part is part of the meN- verbal prefix system. It usually marks an active verb, especially when the verb takes a direct object.

Here, the sentence has:

• Saya = subject
• membaca = active verb
• petunjuk itu = object

So membaca tells you that the subject is actively doing the action of reading something.

A useful pattern is:

• menulis = to write
• membeli = to buy
• membaca = to read

All of these are common active verb forms.

Indonesian verbs usually do not change form for tense.
That means membaca can mean:

• read
• am reading
• was reading
• will read

The exact time is usually understood from:

• context
• time words
• extra markers

For example:

• Saya sedang membaca petunjuk itu. = I am reading that instruction/those instructions.
• Saya sudah membaca petunjuk itu. = I have already read that instruction/those instructions.
• Saya akan membaca petunjuk itu. = I will read that instruction/those instructions.

So the basic sentence leaves the time unspecified unless context makes it clear.

In Indonesian, demonstratives like ini and itu usually come after the noun.

So:

• petunjuk ini = this instruction / these instructions
• petunjuk itu = that instruction / those instructions

This is different from English, where this and that come before the noun.

So petunjuk itu is the normal Indonesian order, not itu petunjuk in this kind of sentence.

It can mean either one, depending on context.

Indonesian nouns usually do not change form for singular vs. plural. So:

• petunjuk can mean instruction, instructions, guidance, or directions, depending on the situation.

If someone wants to make plurality very clear, they can use reduplication:

• petunjuk-petunjuk itu = those instructions

But in many real sentences, Indonesian simply leaves number to context.

Yes, very often.

Although itu literally means that, in many contexts it also helps make a noun feel specific or already known, which is sometimes close to English the.

So petunjuk itu can feel like:

• that instruction
• those instructions
• or sometimes simply the instruction(s)

Which translation fits best depends on context.

This is one reason Indonesian learners sometimes feel that itu is doing more than one job.

Both saya and aku can mean I, but they differ in style and register.

• saya = more neutral, polite, standard
• aku = more informal, personal, casual

So:

• Saya membaca petunjuk itu. sounds neutral and standard.
• Aku membaca petunjuk itu. sounds more casual and intimate.

Textbooks usually introduce saya first because it works well in more situations.

Yes. This sentence uses the very common pattern:

• Subject + Verb + Object

So:

• Saya = subject
• membaca = verb
• petunjuk itu = object

That basic order is very common in Indonesian.

However, Indonesian also allows other structures in some contexts, especially for emphasis or in passive sentences. For example:

• Petunjuk itu saya baca. = That instruction/those instructions, I read.
• Petunjuk itu dibaca oleh saya. = That instruction/those instructions were read by me.

But the original sentence is the most straightforward and natural basic form.

To make it negative, you use tidak before the verb:

• Saya tidak membaca petunjuk itu.

That means I do not read / am not reading / did not read / will not read that instruction/those instructions, depending on context.

A simple rule:

• tidak is used to negate verbs and adjectives
• bukan is usually used to negate nouns or noun phrases

So here, because membaca is a verb, tidak is the correct choice.