Ta koperta jest za mała na wydruk i dwa dokumenty.

Because koperta is a feminine noun in Polish.

Polish demonstratives change for gender:

• ten = masculine
• ta = feminine
• to = neuter

So:

• ta koperta = this envelope

You can often tell that a noun is feminine if it ends in -a, and koperta does.

For the same reason: koperta is feminine, so the adjective must agree with it.

Polish adjectives change to match the noun in:

• gender
• number
• case

Here:

• koperta = feminine singular
• so mały becomes mała

Compare:

• ten dokument jest za mały = this document is too small
• ta koperta jest za mała = this envelope is too small
• to pudełko jest za małe = this box is too small

Here za means too.

So:

• mała = small
• za mała = too small

This is a very common Polish pattern:

• za duży = too big
• za ciężki = too heavy
• za drogi = too expensive

So jest za mała means is too small.

In this sentence, na means something like for or to fit.

So:

• za mała na wydruk i dwa dokumenty = too small for a printout and two documents

This is a common Polish structure:

• za mały na coś = too small for something
• za ciężki na coś = too heavy for something
• dobry na coś = good for something

So na introduces the thing the envelope is too small for.

Here na takes the accusative case.

That is why the sentence uses:

• wydruk
• dwa dokumenty

These are the accusative forms.

For inanimate masculine nouns like wydruk, the accusative singular is often the same as the nominative singular, so it looks unchanged.

Compare:

• nominative: wydruk
• accusative: wydruk

So even though the form looks the same, it is still accusative here.

Because after na in this meaning, Polish uses the accusative, not the genitive.

The noun wydruk is a masculine inanimate noun, and in the singular its accusative form is the same as its nominative form.

So:

• nominative: ten wydruk
• accusative: na wydruk

If it were genitive, then you would expect wydruku, but that is not the case needed here.

Because dokument is masculine inanimate.

Polish has different forms for two:

• dwa for masculine and neuter nouns
• dwie for feminine nouns

So:

• dwa dokumenty = two documents
• dwie koperty = two envelopes

Since dokument is masculine, dwa is correct.

After dwa, trzy, and cztery, Polish normally uses the nominative/accusative plural form of the noun, not the genitive plural.

So:

• dwa dokumenty = correct
• trzy dokumenty = correct
• cztery dokumenty = correct

But with five and above, Polish usually switches to the genitive plural:

• pięć dokumentów

So the pattern is:

• dwa / trzy / cztery dokumenty
• pięć dokumentów

Not really. I simply means and, and both nouns are still governed by na.

So na applies to both parts:

• na wydruk
• na dwa dokumenty

Polish often does this without repeating the preposition:

• na wydruk i dwa dokumenty

You could repeat it for emphasis, but normally you do not:

• na wydruk i na dwa dokumenty — grammatical, but less natural here

No, Polish word order is fairly flexible, but the original order is the most neutral and natural.

Neutral version:

• Ta koperta jest za mała na wydruk i dwa dokumenty.

You might also hear:

• Na wydruk i dwa dokumenty ta koperta jest za mała.

That version puts more focus on what the envelope is too small for.

So the meaning stays basically the same, but the emphasis changes.

In normal standard Polish, jest should stay.

So the natural sentence is:

• Ta koperta jest za mała na wydruk i dwa dokumenty.

Polish often omits to be in some special styles, like notes, headlines, or very informal fragments, but not in a normal full sentence like this.

So for a learner, it is best to keep jest.

Yes, wydruk is a normal word and usually means a printout or something that has been printed.

It suggests a physical printed page or printed document.

Depending on context, Polish could also use other words, but wydruk is perfectly natural if you mean something like:

• a printed sheet
• a printout from a computer or printer

So the sentence sounds like the envelope is too small to hold:

• one printout
• and two other documents