Fyodorov was forced out of Moscow because of his attempts to employ the “blasphemous” new printing techniques, and found refuge in Poland–Lithuania, first in Zabłudów, then most notably in Ostroh, where he was instrumental in the publication of the Ostrog Bible.

[3] In his other famous book "Ostrog Bible" (1581) he called himself in both Church Slavonic and Greek as "Ivan, son of Feodor (Феодоров сын, Θεοδώρου υἱός), a printer from Moscow".

But when he was living for a long time in the Polish–Lithuanian Commonwealth, he adopted a local Ruthenian style patronymic in Polish spelling "Fedorowicz" and also added a nickname indicating his origin.

In his Latin documents he signed Johannes Theodori Moscus (that is "a Muscovite"[4]), or Ioannes Fedorowicz Moschus, typographus Græcus et Sclavonicus.

As a result of the dialectical replacement of consonant /f/ with /x~xw/ in early East Slavic the first letter F was sometimes changed, so the patronymic became Chwedorowicz or Chodorowicz.

In 1564–5 Fedorov accepted an appointment as a deacon in the church of Saint Nicolas (Gostunsky) in the Moscow Kremlin.

Together with Pyotr Timofeev from Mstislavl (i.e. Mstislavets), he established the Moscow Print Yard and published a number of liturgical works in Church Slavonic using moveable type.

This technical innovation created competition for the Muscovite scribes, who began to persecute Fyodorov and Mstislavets, finally forcing them to flee to the Grand Duchy of Lithuania after their printing workshop had been burned down (an alleged arson, as related by Giles Fletcher in 1591).

Fyodorov moved to Lviv in 1572 and resumed his work as a printer the following year at the Saint Onuphrius Monastery.

In 1575 Fyodorov, now in the service of Prince Konstanty Wasyl Ostrogski, was placed in charge of the Derman Monastery near Dubno; in 1577–9 he established the Ostrog Press, where, in 1581, he published the Ostrog Bible — the first full version of the Bible in Church Slavonic printed in moveable type — as well as a number of other books.

Fyodorov returned to Lviv after a quarrel with Prince Konstantyn Ostrogski, but his attempt to reopen his printing shop was unsuccessful.

Zabłudów, 8 July 1568 – 17 March 1569, 8 unnumbered and 399 numbered leaves sized at least 310 x 194 mm, printed in two colours, at least 31 copies are extant today.

Lviv, 1574, 40 unnumbered leaves, frame (type page) of 127,5 x 63 mm, printed in two colours, edition of probably 2,000 copies, but only a single one is known to have survived (stored in the library of Harvard University).

Ostrog, 1578, 8 unnumbered leaves, frame of 127,5 x 64 mm, printed in one colour, set in two columns (parallel Greek and Slavonic text) for the first time in Fyodorov's books, only one copy is in existence (stored in the State Library of Gotha, East Germany).

Chronology of Andrew Rymsha ("Kotorogo sya m(s)tsa shto za starykh věkov děyelo korotkoye opisaniye").