Certified translations, sometimes referred to as sworn translations, are translations which are required for official use.
A certified translation is a legal document; therefore, it must meet a number of requirements. Most importantly, it must be made by sworn translator, a qualified individual entered into the register of sworn translators kept by the Minister of Justice, who must certify that the text of the translation corresponds to the source text. Moreover, a certified translation must be sealed and signed by a sworn translator.
The competencies of a sworn translator are verified in a demanding, two-part state examination, whose pass rate does not exceed 25% (Marek Kuźniak, Egzamin na tłumacza przysięgłego, C.H. Beck, Warsaw 2013, pp. 6)
Since a certified translation must have an affixed seal and signature of a sworn translator, it is made in paper form. Obviously, the translation may also be scanned and sent by email.