The verdict first, so you skip a wasted morning
An apostille is refused in Cambodia. No counter in Padua, and none elsewhere in Italy, can produce a certificate that Cambodian officials will treat as adequate. Their rule is consular legalisation, an older method built on stacked endorsements rather than a single sheet.
Request an apostille from Italy to Cambodia and an obliging clerk may still print one, because Italian counters serve dozens of destinations daily. Printing it is not the same as it being any use. Once your envelope arrives, the reader judges it by a rulebook that wants a mission stamp.
A chain of two links, joined in order
Link one is an Italian public officer who vouches that the autograph on your certificate belongs to a genuine official. Link two is the diplomatic mission speaking for Cambodia, which vouches for that Italian officer in turn. Neither link means much standing alone.
Joined together, those two links are what document legalisation for Cambodia amounts to. Reverse them and both fail, since a mission will not endorse an autograph nobody has yet verified. Build your calendar around the slower link, which is nearly always the second.
Choosing between two counters in Padua
Which Italian counter you approach hangs on the nature of your paper. Civil and academic records, such as a birth entry, a residence certificate or a university transcript, belong to the Prefettura (Prefecture) in Padua. Judgments, decrees and notarial instruments belong instead to the Procura della Repubblica.
The split turns on who signed, never on what the text says. A registrar, a rector or a municipal officer steers you toward the Prefettura. A magistrate, a court clerk or a notary steers you toward the Procura. Where the letterhead leaves you guessing, telephone and describe the signature block.
Ask the mission before you ask anybody else
Since no Italian authority may grant an apostille for Cambodia, the mission's own instructions become the only rulebook that counts. Write early. Missions differ on whether they accept envelopes by post, whether an appointment is compulsory, and whether they will glance at a scan beforehand.
Put five questions in one message: what may be endorsed, in which language, at what price, over how many working days, and in what form payment must arrive. A written reply outranks any summary you find online, this page included, because staff answer for their own counter.
Fees, timing, and the traps between them
Italian duty is simple enough: €16 a document, with several categories exempt from it. Ask before purchasing the revenue stamp, because one bought in error is money gone. Mission charges are fixed independently, are announced nowhere in Italy, and shift occasionally, so verify them the week you intend to pay.
Anyone reading up on apostille requirements for Cambodia should budget for translation too. Whether one is wanted, and into which language, is settled by the reader abroad rather than by anybody here. Obtain that instruction in writing, then have the translation sworn before the seals go on, never afterwards.