Notes on Williams and Abbot, An Introduction to Bibliographical and Textual Studies, Chapter 5 ("Textual Criticism" (52-75).
In this chapter, they discuss the decisions modern editors must make in order to decide how to set the type for the books they are editing. A modern editor often works from previous print editions unless the text has never been published before, in which case they are producing an "editio princeps" or "first edition." Every printed book has a "first edition," but the Latin term (also abbrev. "ed. prin.") often is used to indicate an incunabular or Early Modern book's first edition. Early Modern editors, who often were the owners of the print shop, tended to take significant liberties when editing manuscripts, as Caxton seems to have done when preparing his Malory edition for the press in 1485. If the Early Modern editors were preparing an edition of a book that already had been printed, they had strong motives to reset their type following the previous edition's text. In fact, if they were reprinting in the same format (i.e., octavo ed. prin. to octavo reprint), they might set their type following their predecessor text character for character, including typographical errors in the text and errors in foliation or pagination (at the top for the reader) and signing (at the bottom for the binder)! Going back to a manuscript copy imposed the additional cost of "casting off" the text of the manuscript to determine where the page breaks would fall. That was the only way the typesetter could tell how many pages he would have enough type to set. As you saw in class, every type font has multiple copies of each letter and punctuation mark, but every font has a finite number of types for each character and that imposes an absolute limit on how many pages of the text could be set at once. Unless the printer walked next door to his competition and asked to borrow a cup of type, that is. (Charles Hinman's work on Jaggard's printing of Shakespeare's First Folio demonstrated that the primary printer shared the massive job with other printers who helped out with the work load, and Caxton was known to have had some editions under his colophon printed "off shore" by the French specialty printer, Collard Mansion.)
Sometimes the urge to reprint the previously set text produced interesting bibliographical challenges. Wynkyn de Worde, Caxton's pressman, who took over Caxton's print shop after his master's death in 1491, reprinted a number of Caxton editions. When he first began, he not only continued using Caxton's colophon image, but he also sometimes reproduced the colophons as Caxton had set them, including the claim that they were printed by Caxton with the year unchanged. This might be shady "marketing" of what we would now call a "knock-off," or it might be a humble homage to his master. Errors or deliberately misleading information in early printed colophons appear to have been common. See Curt F. Bühler, “False Information in the Colophons of Incunabula,” Proceedings of the American Philosophical Society 114:5 (20 October 1970) 398-406.) Available online via EbscoHost: MLA International Bibliography. In his later career, de Worde revolutionized English printing, turning out ten times as many editions as his master (1000+ to Caxton's estimated 102) and introduced important marketing and packaging strategies to make his books affordable and attractive (e.g., the formal title page, frequent use of wood-block illustrations, smaller and more affordable format editions of books previously published in large formats). His most recent biography, by James Moran, calls him "the Father of Fleet Street," for the London location of England's publishing industry in the following centuries.