The parchment and the certificate
The diploma di maturità is handed out once, on heavy paper, and replacing a lost one is slow and awkward. So do not put it in the post. Ask the school that issued it for a certificate drawn from its own records instead. That sheet states that you sat and passed the esame di Stato, in the year the register shows. It carries the head's signature and the school's seal.
Who signs a school paper
The signature is what the whole chain rests on, so look at it closely. It must be an ink signature from someone entitled to sign for the school, with a legible name and a title beside it. Ask the secretariat whose signature they normally use for papers going abroad, because that is the one desks downstream are set up to recognise.
The Prefettura route
A school is a public body, and its papers are office papers. That puts them with the Prefettura, sometimes written Prefecture, rather than with the Procura della Repubblica, which keeps the judicial and notarial pile. So how to legalize a High School Diploma is, in Padua, a question with one answer: the Prefettura di Padova legalises the school signature for use abroad.
When the signature is not on file
The Prefettura works from specimen signatures it already holds. Where a head is newly appointed, or a small school has never sent anything abroad, the specimen may be missing and the counter will say so. That is a delay, not a dead end.
Ring the Prefettura before you queue, give the name of the school and the name of the signatory, and ask whether the specimen is on file. If it is not, ask who has to certify the signature first. Sorting that out by phone is cheaper than discovering it after you have booked embassy legalization of a High School Diploma in Padua.
Marks and transcripts
Universities abroad rarely stop at the diploma. They want the marks as well: subject by subject, with the final grade and the scale it was given on. Order that sheet from the same secretariat, in the same visit, and send both papers through the chain together. One tax stamp and one queue can cover the pair, while two visits cover only one paper each.
Cost and the diary
Only the tax stamp has a settled price. A €16 marca da bollo goes on the Italian file and is sold at any tobacconist. The school may charge for its certificate, and the consulate publishes a fee of its own that it can change without notice. Set aside 10–15 business days for the whole run, or 3–5 business days where the consulate offers a quick lane.
Who asks for it, and what they add
Admissions offices, employers and licensing boards all read this paper for the same reason: to be sure the schooling happened and the grade is real. That is the point of consular legalization of a High School Diploma in Italy. Whether the consular seal is owed at all depends on the destination, so ask the receiving authority and act on the answer they put in writing.
If a sworn version is wanted, have it made before the Prefettura signs, so one stamp lands on both sheets and you legalize a High School Diploma in Padua once. Confirm in writing which language the admissions office reads. Then book embassy attestation of a High School Diploma in Padua on the finished bundle.