Complete Prepress Knowledge for the Graphic Design and Printing Industry

Prepress refers to all technical and creative tasks completed before the actual printing process. It includes typesetting, layout design, image processing, color correction, file preparation, proofing, and plate-making. Prepress is the bridge between graphic design and print production, requiring knowledge of both desktop publishing software and print manufacturing processes.

Many designers entering the prepress field come from purely graphic design backgrounds and lack a formal understanding of printing standards. This often leads to workflow problems, misunderstandings with print technicians, and production errors. Therefore, anyone transitioning from computer-based graphic design to prepress must devote time to learning printing principles and production requirements.

The following content summarizes key knowledge essential for beginners in English-language prepress production.

I. Typography Knowledge

Typography is the art and technique of arranging type to make written language legible, readable, and visually appealing. In English prepress work, typography focuses on typefaces, font categories, sizes, spacing, and layout rules.

1. Typeface Categories

(1) Serif Fonts

Serif fonts feature small decorative strokes at the ends of characters.

Examples:
Times New Roman, Garamond, Baskerville, Georgia

Characteristics:

• Highly readable for long text
• Traditional and formal appearance
• Commonly used in books, newspapers, and magazines

(2) Sans-Serif Fonts

Sans-serif fonts have clean strokes and no decorative endings.

Examples:
Helvetica, Arial, Futura, Calibri

Characteristics:

• Modern, minimalistic look
• Ideal for headings and digital screens
• Frequently used in corporate branding and advertising

(3) Script Fonts

These fonts imitate cursive handwriting.

Examples:
Brush Script, Pacifico, Dancing Script

Characteristics:

• Decorative and elegant
• Not suitable for body text
• Used mostly for invitations, logos, and special designs

(4) Display / Decorative Fonts

Highly stylized fonts meant for large titles or special effects.

Characteristics:

• Strong personality
• Should only be used for short headlines
• Never for paragraphs or long reading

2. Font Sizes

Font size in English typography is measured using the point (pt) system.

• 1 point = 1/72 inch ≈ 0.351 mm

Common font size guidelines:

Digital displays sometimes use pixels (px):

• 1 pt ≈ 1.33 px

3. Layout and Typesetting Rules

Proper typesetting determines the readability and visual quality of printed materials.

Key guidelines:

• Use appropriate page sizes (A4, Letter, etc.)
• Line length should be 50–75 characters for optimal readability
• Line spacing should be 1.2–1.5 times the font size
• Avoid splitting short words between lines
• Keep consistent margins and alignment
• For English text, left-aligned paragraphs are standard
• Avoid decorative fonts in body copy
• Keep punctuation attached to the previous word; do not leave punctuation at line beginnings

II. Paper Knowledge

Paper selection affects ink absorption, color accuracy, sharpness, and the final printed effect. Understanding paper types and weights is essential in prepress.

1. Paper Composition

Paper is made from plant fibers mixed with chemicals and additives.

Main components:

• Fiber

Common sources:

• Wood pulp
• Cotton
• Bamboo
• Recycled fiber

Different fibers affect paper strength, brightness, and smoothness.

Improve:

• Opacity
• Flexibility
• Smoothness
• Printability

Examples:

• Calcium carbonate
• Kaolin clay
• Talc

• Sizing Agents
Increase water resistance and prevent ink bleeding.

Examples:

• Starch
• Resin
• Alum

• Dyes & Pigments
Used to control whiteness or add color.

2. Paper Formats

Paper for printing is available in two major forms:

(1) Sheet Paper (Cut Sheets)

Used in offset printing and general print shops.
Common international sizes (ISO 216):

• A4: 210 × 297 mm
• A3: 297 × 420 mm
• A2: 420 × 594 mm
• A1: 594 × 841 mm
• A0: 841 × 1189 mm

(2) Roll Paper

Used in high-speed web presses for:

• Newspapers
• Magazines
• Packaging
• Labels

3. Paper Weight (GSM)

Paper is graded by grams per square meter (gsm).

Common weights:

Rule:

• ≤200 gsm = paper
• >200 gsm = paperboard

III. Prepress Layout, File Preparation & Printing Requirements

Prepress ensures that a digital design becomes a properly printed product without errors.

1. Document Setup

Before designing:

• Set the correct final page size
• Use CMYK color mode for printing
• Add 3–5 mm bleeds around all edges
• Maintain a safe zone away from edges
• Use correct resolution images

2. Image Requirements

• Print images must be 300 dpi
• Use TIFF, PSD, or high-quality JPEG
• Avoid low-resolution internet images
• Avoid mixing RGB images in a CMYK project

3. Color Management

• Use standardized color profiles (FOGRA39, SWOP, GRACoL)
• Soft-proof colors on calibrated monitors
• Avoid RGB transparency when exporting print PDFs

4. Preflight Checking

Before plate-making, verify:

• Missing fonts
• Wrong color modes
• Low-resolution images
• Incorrect overprint settings
• Transparency issues
• Bleeds and trim marks
• Page alignment
• Imposition accuracy

5. PDF Output and Plate Making

• Export as PDF/X-1a or PDF/X-4
• Include bleeds and crop marks
• Ensure all fonts are outlined or embedded
• Confirm CMYK color values
• Check trapping and overprinting settings
• Verify plates before printing