Pre-Press Complete Guide

Every pre-press problem begins in the document, either the page size is wrong, the colour space was never set correctly, or the document was built for screen rather than print. Setting up the document correctly before any design work begins prevents the majority of pre-press corrections that delay production and add cost.

Page size · trim size vs document size

The document page size in InDesign or Illustrator should be set to the final trim size of the printed piece, the size after cutting. Bleed is added as a separate parameter outside the page boundary, not as extra page size. Setting the document page to include bleed is a common error that causes the press room to receive a file with incorrect dimensions.

Colour mode · set CMYK from the start

Set the document colour mode to CMYK before placing any images or creating any colour swatches. In InDesign: File → Document Setup → Intent → Print. In Illustrator: File → Document Color Mode → CMYK. Building a document in RGB and converting to CMYK at export introduces unpredictable colour shifts, colours that look correct on screen in RGB shift noticeably when the RIP converts them to CMYK. Starting in CMYK means every colour decision is made in the print colour space from the beginning.

Units · use millimetres, not pixels

Set document units to millimetres for all print work. Pixels are a screen measurement and have no fixed physical size, they depend on the output device resolution. A designer who specifies elements in pixels and then converts at export introduces approximation errors into critical measurements like bleed, margins, and object positioning. Millimetres throughout, from first page to final export.

Every printed and cut piece has three zones that the designer must understand and account for. Misunderstanding any one of these three zones produces a visibly defective printed piece, white edges where colour should reach the trim, or important content cut off by the guillotine.

Bleed · 3mm on all sides

Bleed is the extension of background colours, images, and patterns beyond the trim edge. When a printed sheet is cut by a guillotine, the cut is accurate to within approximately ±0.5–1.0mm. Without bleed, a guillotine that cuts 0.5mm outside the trim line would reveal a white strip of unprinted paper at the edge, a visible defect on any piece where colour is intended to reach the edge. With 3mm of bleed, even a 1mm cutting error produces no white edge.

The standard bleed for offset sheetfed printing in India is 3mm on all four sides. For some packaging applications (particularly those with very tight register) 5mm bleed may be specified. Always confirm the required bleed with the press room before starting the design, never assume.

Trim line · where the guillotine cuts

The trim line is the final finished size of the printed piece. In InDesign, the trim line is the page boundary. Crop marks in the exported PDF mark this line for the press room's cutting equipment. Everything outside the trim line will be cut away, bleed included.

Safety margin · 5mm inside the trim

The safety margin (also called the live area or keep-away zone) is the zone inside the trim where all critical content must be placed. Any text, logo, important image element, or essential graphic that falls within 5mm of the trim line risks being partially cut off, either because of cutting tolerance or because the finished piece will be bound or folded and the content will be covered. The rule is absolute: nothing important within 5mm of the trim edge.

Every colour in a print file must be defined in CMYK, the four-colour system that the press prints. Files containing RGB colours, Lab colours, or colours without an embedded ICC profile create uncertainty at the RIP stage: the press room's software must guess how to convert those colours to CMYK, using its default settings which may not reflect the intended colour appearance.

The correct colour workflow

• Document colour mode: CMYK, set from the start, before any design work begins
• Output ICC profile: ISOcoated_v2 (for coated paper) or ISOcoated_v2 300% (for packaging), the standard for Indian commercial and packaging offset printing. Download free from the ECI (European Colour Initiative) website.
• All placed images: converted to CMYK before placing, convert images in Photoshop using Edit → Convert to Profile → ISOcoated_v2 with Relative Colorimetric or Perceptual rendering intent. Do not rely on InDesign to convert placed RGB images at export.
• Spot colours: correctly defined in swatches as Spot, not Process, Pantone swatches must be set to Spot Colour in the swatch options. A Pantone colour set as Process will be printed as CMYK, not as a dedicated spot ink unit.

Total ink coverage (TIC) · the limit that prevents drying failures

Total ink coverage is the sum of CMYK percentages at any point on the design. A point printed as C80 M70 Y70 K100 has a TIC of 320%. The maximum TIC for standard coated paper in offset printing is 300–320%. Exceeding this limit causes slow drying, setoff in the delivery pile, and post-finishing failures including lamination delamination. Check TIC in InDesign using the Separations Preview panel with Total Ink Coverage display. Any area exceeding the specified limit must be adjusted in the file before submission.

Image resolution determines how much detail a raster image contains at its output size. For offset printing, the required image resolution is determined by the halftone screen ruling of the press. The rule: image resolution in PPI (pixels per inch) should be 1.5–2× the halftone screen ruling in LPI (lines per inch).

The resolution rule

• Standard 150 LPI offset printing (most Indian commercial print): minimum 225 PPI, recommended 300 PPI at final print size
• Fine 175 LPI offset printing (premium commercial, quality packaging): minimum 263 PPI, recommended 350 PPI
• Wide-format inkjet (posters, banners at viewing distance 1m+): 72–150 PPI at final print size is often sufficient, resolution requirement decreases as viewing distance increases

Critical: resolution at final print size, not at placed size

An image's resolution changes when it is scaled in InDesign. A 300 PPI image at 100% size becomes 150 PPI when scaled to 200%, below the minimum for quality offset printing. Always check effective resolution in InDesign's Links panel (Window → Links → select image → Info pane shows Effective PPI). This is the resolution the image will actually be printed at, accounting for any scaling applied in the layout.

Font errors are the second most common pre-press problem in Indian print production. A file that uses fonts not available to the press room's system will either fail to process entirely, substitute a different font silently, or produce PDF export errors. All three outcomes are expensive to discover after the fact.

Embedding vs outlining · two approaches

• Embedding (preferred for PDF/X), when exporting to PDF/X-4, InDesign automatically embeds all fonts used in the document into the PDF file. The press room does not need to have the fonts installed, the font data is contained within the PDF. This is the preferred approach and the standard for PDF/X file exchange. Verify embedding in Acrobat Pro: File → Properties → Fonts tab, every font should show "Embedded" or "Embedded Subset."
• Converting to outlines (alternative for Illustrator files), converting all text to outlines (Type → Create Outlines in Illustrator) removes the font data entirely and replaces text characters with vector paths. The advantage: no font dependency. The disadvantage: the text can no longer be edited, and extremely fine type (below 6pt) can lose sharpness at the outline conversion. Only convert to outlines when sharing working files rather than PDFs, or when a specific font cannot be embedded for licensing reasons.

Font sizes and print legibility

• Minimum body text for reading comfort: 7–8pt (smaller is physically readable but uncomfortable)
• Minimum legal text (terms and conditions, disclaimer): 5–6pt, the legal minimum for print, used for fine print only
• Minimum for reversed text (white on dark): add 1–2pt to the above minimums, reversed text requires larger sizes than positive text for the same legibility because the ink spread fills in the counters of small reversed characters
• Minimum for text printed in pure CMY (no black): add 1pt, CMY composite black text is prone to colour fringe from register variation and must be larger than single-colour black text for clean appearance

PDF/X is the international standard for the exchange of print-ready PDF files. It mandates a specific set of requirements, embedded fonts, CMYK colour space, embedded output intent ICC profile, and no RGB or device-dependent colours, that ensure the file can be processed reliably by any compliant RIP without press-room-specific adjustments. PDF/X-4 is the current recommended standard, supporting live transparency (unlike the older PDF/X-1a which requires flattening).

InDesign PDF/X-4 export settings

Verifying the exported PDF in Acrobat Pro

• Output Preview (Tools → Print Production → Output Preview), toggle separations to verify: (a) all colours are in CMYK with no RGB objects, (b) spot colour channels appear as separate separations, (c) total ink coverage does not exceed the specified limit in any area
• Fonts (File → Properties → Fonts), every font listed should show "Embedded" or "Embedded Subset"
• Bleed verification, zoom to 100% at each corner and confirm that the background colour extends beyond the crop marks by 3mm on all sides
• PDF/X compliance (Tools → Print Production → Preflight → PDF/X-4 profile), run the PDF/X-4 profile check. Zero errors means the file meets the standard.

Preflight is the process of systematically checking a print file against a defined set of technical requirements before it is sent to the press room. A thorough preflight catches errors that would otherwise reach the press, saving plate costs, paper waste, and the delay of a reprint. Every file sent for production should pass a designer-side preflight before submission, and will be preflighted again by the press room on receipt.

Designer preflight checklist · check every item before submitting

Proofing is the verification step between the approved digital file and the production press run. It is the last practical point at which errors can be caught before the full cost of plate making, press makeready, and substrate commitment is incurred. The type of proof required depends on the job value, colour criticality, and client sign-off requirements.

How to evaluate a proof correctly

• Always evaluate proofs under a D50 (5000 Kelvin) standard light source, a calibrated light booth. Do not evaluate under office fluorescent, window light, or incandescent.
• Do not compare the proof to a monitor, compare it to the previous approved sample or previous printed job if this is a repeat.
• Mark corrections clearly in writing with page reference and specific location (e.g. "Page 3, header text, 'Anvils' should be 'Anvil's'"). Do not annotate with "as discussed", all corrections must be explicit.
• Sign the approved proof with name, date, and "Approved for print" or "Approved with corrections." The signed proof is the legal agreement between client and printer on what the press should match.