Designing for Offset & Colour Profiles for Print

Every print file problem that reaches a press room could have been prevented at the document setup stage. The document dimensions, colour mode, bleed, and margins must be set correctly before any design work begins, retrofitting these settings after a design is complete is inefficient and error-prone. The five minutes spent setting up the document correctly at the start prevents hours of correction work before print.

Document dimensions · always specify the finished trim size

Set the document page size to the finished trim size, the size of the printed piece after cutting. Do not add bleed to the document size. Bleed is set separately in the document bleed settings and extends outside the page boundary. When you hand a file to a press room and the page size is the trim size, all positioning and margin calculations are clean and unambiguous. When the page size includes the bleed, measurements become confusing and errors multiply.

Bleed · 3mm on all sides (standard)

Bleed is the extension of background colours, images, and any design element that touches the page edge, beyond the trim line. After printing, the sheet is cut to the trim line, a small amount of cutting variation (typically ±0.5–1.5mm on a well-maintained guillotine) means the cut line does not fall exactly on the trim mark. If a background colour ends at the trim line, cutting variation will leave a thin white paper edge visible on finished pieces. The 3mm bleed extension ensures that even with maximum cutting variation, the background colour extends fully to the cut edge.

3mm is the standard bleed for commercial print in India. For packaging, bleed requirements differ, particularly at fold lines. See the Folding Cartons and Packaging Design articles for packaging-specific bleed requirements.

Safety margin · 5mm minimum from trim

The safety margin (also called the live area or safe zone) is the area inside the trim where all critical content, text, logos, barcodes, legal declarations, key imagery, must sit. Content placed between the trim line and the safety margin risks being partially cut away if cutting variation moves the cut closer to the design than expected. The standard safety margin for commercial print is 5mm from the trim edge on all sides.

5mm is the minimum. For small formats (business cards, small brochures) where 5mm would consume a disproportionate amount of the design area, a pragmatic minimum of 3mm is sometimes used, but this requires careful quality control of the cutting process. For packaging cartons, safety margins from both cut edges and crease lines must be observed, see the Folding Cartons article for the specific values.

Slug area

The slug area is outside the bleed, used for production notes, job identifiers, colour bars, and registration marks. Slug content is cut away completely in production, it never appears on the finished piece. Use the slug area to place the colour bar, the job name, the date, the version number, and any notes for the pre-press team. Keep the slug clean and unambiguous, a well-organised slug saves significant pre-press communication time.

Every element in a print file must be in the correct colour mode. The press prints with CMYK inks (and spot colours where specified), any RGB element that reaches the press room without conversion will be converted by the RIP, often with unpredictable results. RGB elements in a print file are one of the most common causes of colour surprises in Indian production, images that look correct on screen printing darker, more saturated, or with a different hue than the designer expected.

When to use CMYK

All print files for offset production should be in CMYK. All placed images (photographs, illustrations) should be converted to CMYK before placing in InDesign or Illustrator. Use the ISOcoated_v2 or PSO Coated v3 (Fogra51) CMYK working space for images placed in press-destined artwork, these profiles define what CMYK values mean in the context of ISO 12647-2 coated paper offset printing. Convert images in Photoshop using Edit → Convert to Profile, selecting the appropriate output profile.

When to use spot colours

Specify spot colours (Pantone solid coated) for any colour that must be reproduced with precision beyond what CMYK process printing can achieve, typically brand colours for large corporate clients, metallic inks (gold, silver, bronze), neon/fluorescent inks, and any colour that requires absolutely consistent reproduction across multiple print runs and multiple press rooms. Spot colours are printed with pre-mixed inks from a separate ink unit, producing a single colour from one ink rather than approximating it from four-colour process.

When specifying a spot colour, also specify a CMYK equivalent for any situation where the press does not have a spot unit available, or where the job will go to multiple press rooms with different unit counts. The CMYK equivalent will never match the spot colour exactly, but it provides a usable fallback.

RGB in print files · never acceptable for final output

RGB colour mode is for screens, not for print. An RGB image in a print file will be converted to CMYK by the RIP at the press room, typically using a generic conversion that does not account for the specific press and paper combination. The result is unpredictable. Convert all images to CMYK before delivering to the press room. The only exception is files destined for digital printing systems that accept RGB input natively, confirm with the specific digital press operator before delivering RGB files.

Black in print files can be specified as either 100K (single-colour black, using only the black ink) or as "rich black", a combination of CMYK inks that produces a deeper, denser black than 100K alone. The choice between them depends on the size of the element and the application.

Overprint controls whether an object prints over (overprint) or knocks out of (knockout) the objects beneath it. When an object overprints, its ink is printed on top of any ink already on that area of the plate, the colours mix optically. When an object knocks out, a hole is cut in the background to the exact shape of the overprinting object, so only the foreground colour ink prints in that area. Most elements in a file should be set to knockout, the correct default for almost all print design. Overprint is used in specific, intentional situations.

When overprint is correct

• Black text and black keylines always overprint, black is set to overprint over all other colours by default in InDesign and Illustrator. This prevents the white knockout gap that would appear between the text edge and the background colour due to trapping gaps. A black keyline that knocks out shows a faint halo if there is any misregister.
• Spot UV and varnish layers, varnish and UV coating layers must be set to overprint so they print over the underlying artwork rather than knocking it out.
• Trapping elements, thin trapping strokes added to prevent misregister gaps between adjacent colours must overprint.

When overprint causes errors

• Yellow text or elements overprinting a background, yellow set to overprint over a dark background will appear much darker than intended because the yellow mixes with the dark ink below it.
• White elements set to overprint, a white object set to overprint disappears entirely in print, because white ink (no ink at all in offset) overprinted over any colour simply does not print, the white is invisible. White objects must always knockout. This is the most common overprint error in Indian design files.
• Coloured text over a different colour background, coloured text set to overprint changes colour because it mixes optically with the background ink below it.

PDF/X is an ISO standard subset of PDF specifically designed for reliable print exchange, it specifies which PDF features are permitted and which are prohibited to ensure the file can be processed correctly by any compliant RIP. PDF/X-4 is the current recommended standard for offset printing in India and globally, it supports live transparency (eliminating transparency flattening artefacts that plagued earlier PDF/X-1a files) and CMYK plus spot colours.

InDesign PDF/X-4 export settings

• Standards: PDF/X-4:2008
• Compatibility: Acrobat 7 (PDF 1.6) or higher
• Compression: images: JPEG maximum or ZIP for lossless. Monochrome: CCITT Group 4. Do not downsample images, maintain native 300 PPI resolution
• Marks and bleeds: use document bleed settings (3mm), include crop marks and registration marks, colour bars optional but recommended for press room
• Output: colour conversion: No Conversion. Profile inclusion: Include Destination Profile. Output intent: select the correct ICC output profile (ISOcoated_v2 or PSO Coated v3 for standard coated offset)
• Advanced: OPI: off. Transparency flattening: not required for PDF/X-4 (live transparency preserved)
• Preflight: run the Press Quality preflight profile before export and resolve all errors

An ICC colour profile is a file that describes the colour characteristics of a device or colour space, how the device reproduces colour, what its gamut is, and how its colour values map to device-independent colour coordinates. ICC profiles are the foundation of colour management: they allow software to translate colours accurately from one device to another, from camera to screen, from screen to proof, from proof to press.

Without ICC profiles, a CMYK value of C50 M30 Y70 K0 might look like a slightly different olive green on your monitor, on the proof, and on the press, because each device has its own colour response. With correctly assigned ICC profiles, the colour management system translates the values so the green looks the same on all three. This translation is what colour management does, and ICC profiles are the data files that make it possible.

The profiles used in Indian offset production

Soft proofing is the on-screen simulation of how the artwork will look when printed on a specific press with a specific substrate. It uses the output ICC profile to simulate the press's colour reproduction on the monitor, showing the designer how colours will shift in the conversion from screen RGB to press CMYK, before any ink is printed. A calibrated soft proof is the most immediate, lowest-cost way for a designer to verify colour before committing to a physical proof.

Setting up soft proofing in Adobe applications

In Photoshop or InDesign, soft proofing is enabled through the View menu. The process is the same in both applications:

• Step 1: ensure your monitor is hardware-calibrated (see Proofing article for calibration requirements). Soft proofing on an uncalibrated monitor is not meaningful, the simulation is built on an incorrect baseline.
• Step 2: in Photoshop: View → Proof Setup → Custom. Select the target output profile (ISOcoated_v2 or PSO Coated v3). Rendering intent: Relative Colorimetric with Black Point Compensation for most print work. Enable "Simulate Paper Colour" to include the paper white simulation.
• Step 3: activate: View → Proof Colors (Ctrl+Y / Cmd+Y). The display now shows the simulated print appearance. Toggle on and off to compare the screen appearance with the simulated print appearance.

What to look for in a soft proof

• Colour shift in out-of-gamut colours, saturated RGB colours that fall outside the CMYK gamut will shift noticeably in soft proof. Vivid blues, electric greens, and neon colours are most commonly affected. If a colour shifts significantly, either redesign to use in-gamut colours, or accept that the printed result will differ from the screen appearance.
• Shadow detail, very dark areas may lose detail when converted to CMYK due to maximum ink coverage limits. Check that shadow areas in photographs remain open in soft proof.
• Paper white simulation, enabling paper white simulation shows the off-white appearance of coated paper rather than the monitor's bright white. Colours appear slightly warmer and less bright, this is the correct simulated appearance of print on coated paper.