Learn Hardcore Spanish (Spain): Copia este texto y pégalo en el documento nuevo. - Copy this text and paste it into the new document.

They are affirmative commands in the tú form (informal singular). Copia is the tú imperative of copiar. pégalo is the tú imperative of pegar plus the direct object pronoun lo attached to the end.

Why does pégalo have an accent?

When you attach a pronoun to an affirmative command, the stress can shift. The base command is pega (stress on the first syllable: PE-ga). Adding lo would produce pegalo, whose default stress would fall on the penultimate syllable (ga). To keep the original stress, you add a written accent: pégalo.

What does lo refer to here? Why not le or la?

lo is the masculine singular direct object pronoun, referring to este texto (masculine singular).

la would be used for a feminine singular direct object (e.g., la carta → pégala).
le is an indirect object pronoun; in Spain, some speakers use leísmo with masculine people (e.g., Le vi), but not with inanimate objects like texto, so lo is correct here.

Where do object pronouns go with commands?

Affirmative commands: attach them to the end of the verb (e.g., pégalo).
Negative commands: place them before the verb (e.g., No lo pegues en el documento nuevo).
This is why you cannot write pega lo in an affirmative command; it must be pégalo.

Can I mix a full noun with a pronoun like this (noun after the first verb, pronoun after the second)?

Yes, that’s natural and common to avoid repeating the whole noun phrase: Copia este texto y pégalo… The pronoun lo clearly points back to este texto.

How would I say this to someone formally or to more than one person (Spain vs. Latin America)?

Usted (formal singular): Copie este texto y péguelo en el documento nuevo.
Vosotros (informal plural, Spain): Copiad este texto y pegadlo en el documento nuevo.
Ustedes (plural, Spain formal and all-purpose plural in Latin America): Copien este texto y péguenlo en el documento nuevo.

Why is it en el documento and not al documento?

In computer contexts, the normal collocation is pegar algo en un documento/una celda/una caja de texto (paste in/into). Pegar algo a tends to suggest physically sticking something to a surface (with glue, tape, etc.). So here en is the idiomatic choice.

Is there any difference between documento nuevo and nuevo documento?

Both are possible, but there’s a nuance:

documento nuevo often emphasizes that the document is brand-new (unused).
nuevo documento can suggest “a new/another document” (new to you, not necessarily brand-new as an object).
In UI/instructions, you’ll see both; context usually makes the meaning clear.

Should este ever carry an accent (éste)?

No here. este is a demonstrative adjective modifying texto, and it is written without an accent. Since 2010, the RAE recommends writing demonstratives without accents even when they function as pronouns; an accent is only optional in rare cases of ambiguity.

Why is the conjunction y used and not e?

Spanish changes y to e only before a following word that begins with the vowel sound i- (spelled i- or hi-), e.g., padres e hijos, blanco e impoluto. Here the next word is pégalo (starts with p), so y stays as y. Note that with words beginning hie- (e.g., hielo, hierro), the sound is [je], so you keep y: agua y hielo.

How would the pronoun change with different objects?

It agrees in gender and number with the direct object:

Masculine singular: texto → pégalo
Feminine singular: imagen → pégala
Masculine plural: archivos → pégalos
Feminine plural: frases → pégalas
If you also add a pronoun to the first verb: Cópialas y pégalas (for las frases), with accents to maintain stress: cópialas, pégalas.

Does pegar have other meanings I should know about?

Yes. Besides “to paste” (in computing), pegar also means “to stick/glue” (physically) and “to hit/strike.” Context disambiguates: in tech contexts with copiar y pegar, it’s unequivocally “copy and paste.”