Here's a mistake made by the majority of businesses producing their first catalog: they design a PDF, it looks great on screen, and they send the same file to both the printer and their wholesale buyers by email. The printed version comes back with colours that look darker and muddier than expected. The emailed version is 28MB and nobody can open it. Both problems were preventable.
Print and digital PDFs are different file types serving different purposes. Understanding why — in plain, non-technical language — saves you from expensive reprints, embarrassing file sizes, and color surprises.
CMYK vs RGB: The Colour Mode Difference
Every colour on a screen is created by combining Red, Green, and Blue light — this is the RGB colour model. Your monitor, your phone screen, and your TV all work this way. Screens emit light, and you mix light to make colours.
Commercial printing works differently. Printers use four ink colours — Cyan, Magenta, Yellow, and Black (CMYK) — and mix them physically on paper to create the range of colours you see. Ink absorbs light rather than emitting it, and the physics of mixing inks produces a narrower range of achievable colours than mixing light.
This means a vivid teal that looks electric on screen may print as a slightly duller, greener version of itself. Bright oranges and certain purples are particularly prone to shifting. A professional print-ready catalog is built in CMYK from the start, with colour values calibrated specifically for printing — not converted from RGB at the last minute. Late-stage conversion from RGB to CMYK is what produces the colour surprises most businesses encounter on their first print run.
Resolution: 300 DPI vs 150 DPI
DPI stands for dots per inch — it's the measure of how much detail is packed into a given area of an image. Print requires high resolution because the dots of ink are physically placed on paper at fine detail. The standard for commercial print is 300 DPI — anything less produces images that look soft or pixelated when printed.
For digital viewing on a screen, this level of detail is unnecessary and actively harmful to usability. Screens display at 72–96 DPI, and most modern displays at 144 DPI for retina/HiDPI. A 300 DPI image on a 72 DPI screen just means a very large file with no visible benefit. A typical 32-page catalog at 300 DPI and CMYK produces a file of 15–30 MB — too large for email, slow to download, and cumbersome for buyers to open on mobile. The same catalog at 150 DPI in RGB, with digital compression applied, typically comes in at 3–8 MB — fast to download, easy to email, no visible quality difference on screen.
Bleed and Crop Marks: Print-Only Specifications
When you print a document, the paper is printed slightly larger than the final size and then cut down. "Bleed" is the extra border — typically 3mm on each edge — of background colour or imagery that extends beyond the final cut line. Without bleed, a slight misalignment in cutting produces a thin white edge on the trimmed page, which looks unprofessional.
Crop marks are the small lines printed in the margin of the large sheet that tell the cutting machine exactly where to cut. A properly prepared print file includes both bleed and crop marks. A digital PDF destined for screen use has neither — they're irrelevant and visual clutter in a digital document. A professional print-ready export sets up bleed and crop marks automatically; a digital export does not.
File Size: Why It Matters More Than You Think
A 28MB PDF catalog sent by email will bounce from many corporate email servers, which typically impose a 10–20MB attachment limit. Even if it gets through, a buyer on a mobile connection who clicks your email attachment and waits 40 seconds for it to load is likely to abandon it and never return.
File size in a digital PDF is managed through several mechanisms: lower resolution images, aggressive JPEG compression for photography, font subsetting (including only the characters actually used in the document rather than the full typeface), and structured compression algorithms. None of these affect visual quality on screen — but they dramatically reduce file size. A 28MB print PDF routinely becomes a 4MB digital PDF with correct export settings, with no detectable difference in on-screen appearance.
The Correct Production Workflow
The professional approach is to design the catalog once — in a program like Adobe InDesign — and then export two separate PDFs from the same master document using different export presets.
The print export uses CMYK colour, 300 DPI minimum image resolution, 3mm bleed on all sides, crop marks, embedded fonts, and either the PDF/X-1a or PDF/X-4 standard (both are universally accepted by commercial printers). The digital export uses RGB colour, 150 DPI image resolution, no bleed, no crop marks, compressed images, and web-optimised font handling.
Both files come from the same layout, the same design, the same typography. Nothing is redesigned — only the export settings differ. This is what professional catalog designers do as standard process, and it's included in every project we produce.
How Colour Shifting Happens and How to Prevent It
Even when CMYK values are set correctly, there can be variation between how colours look on your monitor and how they print — because monitors are not calibrated to match any specific printing standard. The most reliable safeguard is to request a physical proof (a single printed copy) from your printer before approving the full print run. This costs a small additional fee but eliminates the risk of reprinting an entire order because the background colour printed too dark.
For brand-critical colours — a specific corporate blue, a recognisable orange — professional designers use Pantone matching as a reference standard. A Pantone colour has a defined, consistent printed value that any printer in the world can match. If colour accuracy is non-negotiable for your brand, discuss Pantone references with your designer and printer before the project begins.
Every catalog we produce at PDFCatalogue includes both a print-ready CMYK file and an optimised digital PDF as standard — not as an add-on. If you'd like to know more about our production process or discuss a project, get in touch.