WHAT ORIGINALS SHOULD YOU USE FOR A SWORN TRANSLATION?
A common issue in sworn translations in Brazil is the original the Public Translator will translate from, and what s/he will attach to the sworn translation.
Things you should know:
A Brazilian Public Translator may translate from any original, for instance, the very original, a notarized/certified copy, a plain copy, a scanned electronic file, a web page, or even a fax, however s/he must mention in the translation what kind of original it was translated from. It will be up to the entity receiving such sworn translation to set the requirements for the original to be translated, in order to determine whether a translation should be accepted or rejected.
A Brazilian Public Translator has no way to tell you what any entity - either in Brazil or elsewhere - accepts or requires. You'll have to ask them about it. It is advisable to get their specifications in writing (e-mail should do), so you won't have the "wrong" document translated on account of bad info from an employee who made a mistake. This will enable you to prove that you followed their instructions.
The Brazilian Public Translator must keep on file all the sworn translations s/he has ever done, however they don't retain copies (not even on electronic files) of any originals. Therefore, if you request a translation from a scanned file, and later find out that the translation must be done from an original, when you provide the original to be translated, it will be a new translation, which will unnecessarily double your expense (discounts are explicitly disallowed by law).
Depending on mutual agreement, a Brazilian Public Translator may draft a sworn translation from a scanned file while the source document is on its way. This expedites matters. In such cases, it is absolutely normal for the Sworn Translator to request an advance payment on the estimated cost for the translation, to prevent a prospect from requesting such draft based on an electronic file from a number of different translators, and eventually closing the deal with (and paying) only one of them.
What you should understand:
Brazilian Law on sworn translations is ancient, Decree 13.609 dates back from October 1943, therefore it precedes photostatic copying, computers, and the Internet. Consequently it naturally assumes that the translation will be done from a paper document, and issued in hard copy. Note that the law only assumes a paper document as source - because no other media existed when it was passed - however it determines that the sworn translation shall be printed on paper.
The Brazilian Public Translator is not competent (in both senses) to ascertain the authenticity of any source document, s/he will merely translate the document presented. According to the Law, the document becomes acceptable when attached to its sworn translation . Hence if a sworn translation is done from a plain copy or a scanned file, and these are not acceptable for the intended purpose, the sworn translation will be useless.
A sworn translation does not replace its original. As explained in the previous item, it (or a copy thereof) is attached to the original document. If the source document is an electronic file, the Public Translator will print it out, stamp and initial it to attach to the translation.
In order to ensure that the original used for translation is legit, depending on the intended purpose, sometimes the original document is required to be certified. This may be done in two ways. In the signatory countries of the Hague Convention, an Apostille is used.
For all non-signatory countries, consular legalization is required, which should be done by the Brazilian diplomatic authorities with jurisdiction over where the document was issued. In that case, this should be done before sending the document for a sworn translation.
In case of translations from Portuguese into other languages, i.e. to submit Brazilian documents in other countries, such translations may be done in compliance to Brazilian law. Some countries accept them, however it must be understood that if they do it, it's on their own will and thanks to the absence of local laws that forbid doing it. However they may require the document/translation to have an Apostille, as provisioned by the Hague Convention (for signatory countries) or consular legalization by the receiving country's diplomatic authorities in Brazil, IF the country is not a signatory of the Hague Convention).
A few specific cases:
Sworn translation of "must carry" documents, e.g. ID, driver's license, or passport. It is not proper, and often impossible for the Sworn Translator to stamp and initial such original documents. On the other hand, such documents might have been seized by competent law enforcement authorities for any reason since they were translated. So obviously submitting a sworn translation attached to a copy thereof will require presenting the original as well.
Sworn translation of hard or expensive to replace documents, e.g. diplomas. The best solution is to provide the Sworn Translator notarized/consularized/apostilled copies of diplomas to attach to the sworn translation. This will preempt any reason to request the original. If you wish, you may provide the Sworn Translator with the original as well, so s/he'll stamp and initial it (on the reverse side, of course!). Then, if you ever need more of these translations in the future, you may ask the Sworn Translator for a transcript (costs 50% of what the translation should cost then), to attach to a notarized/consularized copy of your diploma already having the Sworn Translator's stamp and initials, thus avoiding any chance of it being rejected.
Power of Attorney instruments. At least in Brazil, all notarial offices demand sworn translations of PoA instruments to be done from the very original and attached to it. A certified copy with either an Apostille or consular legalization will NOT be accepted. The reason is simple: if there is anything suspicious, they'll have an original document to be analyzed for forgery, since it may be very expensive, complex, and troublesome to "undo" any misdoings by a spurious proxy on behalf of the grantor.
Originally electronic documents. There is a growing trend in documents originally issued via Internet, which shall only become hard copy when someone prints them. There is no problem in providing the URL for the Sworn Translator to download them, or even to convert them into a PDF file (if it hasn't been done already), and send them for translation. As a general rule such electronic documents usually include instructions for the receiver to check their authenticity online, and these instructions will be included in the sworn translation.
Expiration. I have been asked about how long a sworn translation remains valid until it expires, and also if it ever expires. A sworn translation does not expire, however its role is to render the original document acceptable. If the original document has an expiration date, and it comes by, the sworn translation will lose its function, because its source document will become invalid.
In a nutshell, the Sworn Translator only translates what you order from them, and is in no way responsible for the original being accepted. Therefore it is always advisable to check first what are the requirements on the original document for translation.