What to Check Before Sending a PDF to Print
Printing is unforgiving in a way screens are not. A file that looks perfect in a viewer can come back with grey blacks, missing characters, or white slivers along the edges, and by then it has been paid for. These are the five checks that catch almost everything.
Resolution of placed images
Printing resolves far more detail than any screen. The usual requirement is 300 to 350 DPI at the final printed size, and the trap is that the figure is measured after scaling. A 1000-pixel-wide photograph is 300 DPI at three inches wide and 100 DPI if you stretch it across ten.
Design tools report the effective resolution of each placed image, and it is worth checking every one rather than trusting the originals. An image dragged in from a web page is typically 72 DPI and will look obviously soft on paper even though it looked fine on the monitor it came from.
Line art and logos are the exception that matters most. If a logo is available as a vector file, use it; vectors have no resolution and print at the full precision of the press. A rasterised logo at the wrong size is the single most common thing that makes a professional job look amateur.
Colour space
Screens emit light and mix red, green and blue. Presses lay down ink and mix cyan, magenta, yellow and black. The two ranges overlap but are not the same, and the colours RGB can show that CMYK cannot are exactly the ones people like: saturated oranges, vivid greens, electric blues. They come back noticeably duller.
Converting late, at the printer, means the conversion is done by software with no knowledge of your intent. Converting deliberately, with a soft proof on screen, lets you see the shift and adjust while you still can. Ask the printer which profile they want — Japan Color 2001 Coated is the usual answer for coated stock in Japan.
Black deserves separate attention. Text should be set in pure black — 100% K alone — rather than a mix of all four inks, which looks the same on screen but prints as a slightly blurred, brownish grey when the plates are a hair out of register. Large black areas, by contrast, usually want a rich black mix to avoid looking washed out.
Fonts
Every font must be embedded in the file. If one is not, the printer's system substitutes something else, and the substitute almost never has the same metrics: lines rewrap, a heading spills onto two lines, a table column overflows. The document properties list which fonts are embedded and which are not.
Licensing can block embedding entirely. Some fonts, particularly older commercial Japanese typefaces, carry flags that forbid it, and the exporter will quietly leave them out. If a font refuses to embed, the reliable fix is to convert that text to outlines, which turns the letters into vector shapes that need no font at all.
Outlining is safe but one-way: the text stops being text, so it can no longer be edited, searched, or corrected. Keep an editable master and outline only the copy you send.
Bleed, margins and trim
Anything meant to reach the edge of the finished page has to extend past it, because the cutting blade has a tolerance of a millimetre or so. Japanese printers normally ask for 3 millimetres of bleed on all four sides; the North American convention is an eighth of an inch. Without it, a slight misalignment leaves a white line down one edge.
The same tolerance applies inward. Text and anything else that must not be cut should sit at least 3 millimetres inside the trim line, and more is better. Page numbers tucked tight into a corner are the usual casualty.
Check that the file carries the right boxes as well as the right artwork. The TrimBox should be the finished size and the BleedBox should be larger, and a print-ready export normally includes crop marks outside both. A file exported as plain A4 with artwork running to the edge has no bleed at all, however it looks on screen.
Overprint, transparency and the final look
Overprint tells the press to lay one ink on top of another rather than knocking out the area underneath. It is used deliberately for thin black lines, and it causes accidents when it is set on something light: an object marked to overprint on a dark background can vanish entirely on paper while looking perfectly normal in a viewer.
Transparency — drop shadows, soft blends, partial opacity — has to be flattened into something a press can print, and flattening sometimes produces faint seams where regions were divided. Previewing the flattened result, rather than the live file, is the only way to see these before they are on paper.
A cheap last check is to rasterise the whole document and look at the pages as flat images. Rendering the PDF to images at a high scale collapses every layer, transparency effect and overprint into plain pixels, which is much closer to what the press will do than the layered preview your design tool shows. Flipping through those images at full size catches missing glyphs, vanished objects and resolution problems in a couple of minutes, with no software beyond a browser.
PDF page sizes and paper formats