Full bleed printing refers to the ability to print a document with ink/toner extending all of the way to the edges when a document is trimmed to its finished size. A bleed normally extends ~1/8 inch beyond the edge of the finished document size to allow for registration errors that occur on a printing press and when the document is trimmed to its final size. To reduce toner contamination problems that occur within laser printer engines, and to accommodate crop marks, registration marks, and printers marks which are used in the printing industry, most laser printed full bleeds are printed on oversized paper and then trimmed to size. This is how full bleed printing is accommodated on the LaserWriter 8500.
Page layout applications such as PageMaker, Framemaker, Illustrator, and Quark Xpress assume that the finished document size may differ from the capabilities of the output device. As a result, the page size setup for the output device and the document size are independent within these applications. To accommodate an 8-1/2 X 11 inches full size proof with full bleeds (1/8 inch per side) and printer's marks, the printing device paper size would need to be approximately 1/2 inch larger per side. By allowing the user to independently set the document size and printing device paper size the user is not limited by the capabilities of the output device nor are they forced to print at a reduced size to fit the document with bleed, and the printers marks all on one page. Full bleed capabilities are usually not needed by non-prepress users so the majority of consumer/business applications do not differentiate between the document size and the printer page size.
Although users might like to have edge to edge printing capabilities on their low cost laser printers there are technical limitations that make this feature difficult to implement. In order to print all of the way to the edge the paper handling section of the print engine must register perfectly. Tiny paper registration errors (skew for example) would cause toner to be transferred to the internal workings of the printer wherever the image on the photoconductor didn't match properly with the paper. Unfortunately, the costs for a printer with these capabilities would be extremely high. As a trade off most laser print engine manufacturers hard code a 'protected area' into the print engine controller that prevents imaging within 'X' distance from the edges of the paper. The defined area usually corresponds closely to the paper handling/registration capabilities of the engine. The protected area may differ slightly from the imaginable areas defined by the PPD.