How to prep a file for large-format printing — the honest print shop guide.

Why this matters more than you'd think

A poorly prepped file doesn't fail in production — it fails on the street. The press prints exactly what it gets: if the file is in RGB, blues come out flat; if it's at 72 DPI, text pixelates; if fonts aren't outlined, "Helvetica Neue" becomes "Arial" and nobody warns you.

The other side: a clean file prints, finishes, and ships without anyone needing to call you. The 24-hour rush we offer isn't magic — it's clean files going to press the first time.

This guide walks through what a wholesale printer checks, in the order we check it, before approving a file for production.

1. Document size — at 100%, in inches

The simplest rule, the one most ignored: set up the document at the exact final size of the banner, in inches.

If the final banner is 8 ft. × 3 ft., your document is 96 in. × 36 in. Not 8 × 3 (that's an 8-inch banner). Not 48 × 18 at "double resolution" to "compensate" — that's extra work and opens the door to scaling errors.

Why does this matter? Because DPI (dots per inch) is tied to physical size. A 4,000 × 1,500 px file looks beautiful on screen at 72 DPI, but stretched to 96 × 36 inches at the press, it lands at roughly 42 DPI — pixelated and blurry from 5 ft. away.

The acceptable exception: work at half-size (48 × 18 in.) at 200 DPI. Same total pixel count as the final size at 100 DPI, lighter file. If you do this, mark it clearly on the spec sheet: "document at 50%, scale 200% at RIP."

2. Resolution — 100 DPI minimum at final size

For large-format banners, 100 DPI at final size is the floor. 150 DPI is safer. Beyond 150 DPI doesn't add quality — large-format presses don't resolve more detail than that, and the file just gets heavier.

Critical for raster elements (photos): resolution is measured in the final file at the final size. If your logo arrives as an 800 px PNG and you scale it to 30 inches wide, that logo is at 27 DPI in output — and it'll look pixelated. Replace with a vector version (AI, EPS, SVG) or a larger raster.

3. Color — CMYK, always

Screen color (RGB) and print color (CMYK) are two different universes. Your monitor mixes light; the press mixes ink. A bright RGB cyan doesn't exist in CMYK space — the press approximates it with a flatter mix, and the result can be 20% more muted than what you saw on screen.

What to do:

1. Set the document color mode to CMYK from the start (Edit › Convert to Profile in Photoshop if you started in RGB).
2. For critical brand colors (logos, brand swatches), use exact CMYK values (e.g., C:80 M:50 Y:0 K:0) or Pantone references — don't trust the value your screen shows.
3. For large blacks (backgrounds, oversized type), use rich black (C:60 M:40 Y:40 K:100), not flat K:100. Rich black holds deeper and more uniform outdoors.

If you work in RGB and submit RGB, the press will convert on the fly. It works most of the time — but saturated blues, bright reds, and neon greens never come out the way they looked on screen. If your client signed off on the RGB design, that mismatch is your problem, not the printer's.

4. File formats — what a printer prefers and why

Imperial accepts PDF, AI, EPS, and high-res JPG/PNG. But printers have preferences for a reason:

Practical rule: if your design is mostly text and logos, export vector (PDF/AI/EPS). If it's mostly photo, export TIFF or PDF with the image embedded at the right size and resolution.

Do not send: Word files, PowerPoint, Canva .canva exports, Google Slides exports, or screenshots. Those are presentation formats, not print — their DPI is always too low.

5. Fonts — outline them before export

A font in your file is just a reference — the file says "render this in Helvetica Neue," and it depends on the printer's machine having Helvetica Neue installed. If it doesn't, it substitutes the closest match (often Arial), and your banner ships with the wrong type without anyone noticing until the client sees it.

The fix is to outline fonts before exporting. This converts every letter into a vector shape — it's no longer editable text, it's geometry. The font prints exactly as you designed it, regardless of what fonts the printer has.

How:

• In Illustrator: Type › Create Outlines (Cmd+Shift+O) on all text.
• In InDesign: export to PDF with "subset fonts when percent of characters used is less than: 100%" (Advanced section of the export dialog).
• In Photoshop: rasterize the text layer before exporting (only if the document resolution is high enough).

Common trap: some fonts have license restrictions that prevent embedding in PDF or outlining. If your PDF errors on open, this is usually the cause. Swap the font or license it commercially.

6. Bleed and safe area — the 1.5 in. that saves a reprint

Bleed is the extra design area that extends beyond the final size, so when the printer trims the banner there's no white edge. Safe area is the distance inward from the edge where it's safe to put text and critical elements.

For Imperial banners:

• Bleed: 0.25 in. (6 mm) on all four sides. Extend backgrounds, photos, and color blocks to that edge.
• Safe area / margin: 1.5 in. (38 mm) inward from the final edge. Keep text, logos, and critical elements inside this zone.

Why 1.5 inches? Because the sewn hem takes 1 inch of the edge, and grommets live in that same zone. Anything within 1.5 in. of the edge gets folded into the hem or run through by a grommet. (More on hems and grommets in Banner Finishing 101.)

Setup in Illustrator:

1. Create the document at final size.
2. File › Document Setup › Bleed → 0.25 in. on all four sides.
3. Add a guide 1.5 in. inside each edge as a visible safe area while you design.

7. Design and aesthetics — legibility at the actual distance

A banner is designed to be read from a distance, not to look good on a screen 14 inches from your face. The industry rule:

1 inch of letter height for every 10 feet of viewing distance.

For an outdoor banner viewed at 30 ft., the headline must be at least 3 inches tall. If your client wants "more text," that's not a design problem — it's a hierarchy problem. Something has to be smaller and secondary.

Additional best practices:

• Cap the headline at 7 words or fewer. Beyond that, no one reads it from a car at 35 mph.
• Sans-serif at large sizes. Serifs fall apart at distance. Helvetica, Inter, Roboto, Montserrat — all work.
• Maximum two typefaces. One for headline, another (or the same in a different weight) for body. More is noise.
• High contrast. Dark text on light or vice versa. Red text on a blue background does not read at distance, even though it looks like it does on screen.
• 2–3 main colors max. The client's logo counts. More colors and the banner loses focus.
• White space. Resist the urge to fill every inch. Negative space is what makes the headline pop.

8. The six mistakes that send a file back

What stops a job in pre-press most often, in order of frequency:

1. Document in RGB when CMYK was specified. Result: muted or shifted colors.
2. Image resolution < 100 DPI at final size. Result: visible pixelation.
3. Fonts not outlined and not embedded. Result: substituted typography.
4. No bleed or no safe area. Result: white edge or text cut off by grommets.
5. Logo or photo in low resolution at final size. Result: the rest of the banner is clean, but the logo looks wrong.
6. File at the wrong size (with weird scales like "1:5" undocumented). Result: confusion, client call, day lost.

Each one of these costs between 1 and 24 hours of turnaround. Hit all six rules and your file goes to press the same day.

How Imperial handles incoming files

Every file that arrives at Imperial passes a pre-press check before it goes to press: document size, color mode, DPI at final size, fonts outlined, bleed, safe area, and embedded image resolution. If anything's out of spec, we call you before printing — not after.

For recurring wholesale clients, we send a pre-press spec sheet with empty Illustrator templates (.ai) already configured with the right bleed and safe area for the common sizes. Ask your rep.