One half of this route is settled, the other is not
This route splits cleanly in two. The Sicilian half is fixed: a state office signs your paper, the fee is set, and the steps never change. The far half is the open question. Our own records do not settle whether an apostille for Afghanistan will be taken by the office that has to read your file, so that answer must come from them.
An apostille is one stamp added by a state office. It proves that the signature and seal on your sheet are real, and countries inside the Hague circle take it with nothing further. Italy has sat inside that circle since 1978. Whether the sheet lands the same way at the other end depends on the destination. So treat the far side as a question to answer, not a rule you already know.
What the Sicilian half looks like
These steps are the same whichever answer comes back. Get the sealed original from the office that issued it, whether that is a Comune, a school or a clinic. Administrative papers are stamped by the Prefettura, the arm of the state in each province, while papers signed by a judge or a notary go to the Procura della Repubblica. An apostille from Italy to Afghanistan starts at one of those two desks.
Inside the European Union some public papers now travel with no stamp at all, under EU Regulation 2016/1191. That shortcut reaches member states only, so it does nothing for a file bound for Kabul. Plan on the full stamp here. Ignore advice written for a reader inside the Union, because none of it touches your case.
Getting the answer in writing from the far side
Write to the body that will read your paper and ask two things. Do you accept an apostille, and if not, what do you want instead? Apostille requirements for Afghanistan are set by the receiving side, never by a Sicilian desk. Name the paper, the office it came from and the use you have in mind, then keep their reply. A written answer beats anything you will read on a forum.
If they answer that they want document legalisation for Afghanistan instead, that phrase means a consular chain. The state stamp goes on first, then a signature from the consular service that covers Italy. Ask which mission handles Sicily, what it charges and what it wants to see. Those answers shift from year to year, so work from a fresh one rather than a page you read last winter.
The order of work, and what not to buy yet
Do not order a translation, a courier or a consular slot until that reply lands. The Sicilian stamp is cheap and quick beside those steps, so it is the last thing to worry about. Money goes astray on the parts people guess at. Wait for the written answer, then buy exactly what it names.
A consular chain also changes the running order. The state stamp must be on the sheet before a mission will look at it, and the same mission may want a sworn version alongside. Ask whether they take a sworn version made here, in front of a Tribunale, or want one made locally. That one question decides who you pay, and when.
Cost, waiting and getting the paper there
On the Sicilian side the cost is a €16 tax stamp for each document, with an exempt group set out in law. Buy the stamp at a tobacconist before you queue, because no desk here takes a card. No waiting time is published for the stamp, so leave slack in your plan. Whatever a consular step adds is set and quoted by that office.
Then think about how paper actually reaches your reader. Ask whether they can take delivery in Afghanistan at all, or whether the file should go to a relative or an office in a third country. Ask too whether a scan will hold your place while the paper travels. Files on this route stall on delivery far more often than on any stamp.
Keeping both doors open
Order two sealed originals from the issuing office and have both stamped. If the reply later asks for a consular chain, you already hold a stamped sheet to send on and the second stays in your file. Each sheet takes its own tax stamp, so the price of that cover is small. It is the cheapest hedge on a route whose far end is unsettled.
Keep a written trail as you go: the reply from your reader, the receipts, and a photograph of every stamped sheet. If a clerk in Kabul queries the file, that trail settles most of it in one message. Rebuilding the story from memory months later is what turns a short errand into a long one.