PDF Preflight Checker
A print-ready PDF can be checked entirely in your browser: trim size and bleed (TrimBox/BleedBox), font embedding, effective image resolution and encryption, with the file never leaving your device. Findings are graded error, warning or info, with a downloadable report.
Updated 2026-08-12 · Method version v0.9.0
How to Use
- Click Choose PDF file to upload your artwork; only the first 20 pages are read, files must stay under 50 MB
- The file is parsed in your browser only, nothing is uploaded; wait for Analyzing to finish
- Results list as Error, Warning or Info; click Download report (HTML) to save the full list
- Fix any Error items before printing; passing here is not a press ready guarantee, so keep a human review
Method & Assumptions
Parsing happens entirely in your browser. pdf-lib reads the page boxes (MediaBox/TrimBox/BleedBox) and encryption state, while pdf.js, Mozilla's open-source engine, inspects fonts and images. The file is never uploaded, so confidential artwork and unreleased designs are safe to check.
Bleed is judged as the minimum margin between the TrimBox and the BleedBox or MediaBox. Commercial print generally wants at least 3 mm per side, because cutting has tolerance and a full-bleed design without it ends up with white slivers along the edge. Files without a TrimBox cannot be verified and are flagged as a warning: re-export from layout software with a press preset.
The font check hunts for fonts that are not embedded. When a PDF ships without its fonts, any machine missing them substitutes something else. Spacing drifts, glyphs go missing, and it often surfaces only at the printer's RIP. Press-quality export presets embed everything by default, so an unembedded font usually points to a broken export path.
Effective image resolution is not read from the image's label. The tool follows the transformation matrix (CTM) in the PDF drawing commands and estimates DPI as image pixels divided by the size the image actually occupies on the page. Below 150 DPI is an error and 150–225 a warning, which matches what most printers will accept.
Findings come in three grades. Errors are the problems a printer will most likely bounce the file for; warnings may or may not matter depending on the job, so check them one by one; info items are neutral facts about the file for human judgment. The point is priority, not a false pass/fail comfort.
In the interest of honesty: this is a beta PoC that analyzes the first 20 pages and the first 50 images per page, and files over 50 MB are unsupported. Overprint and transparency flattening, original image color spaces (CMYK/RGB/spot), PDF/X compliance, stroke widths and total ink coverage are out of scope. Treat it as a first self-check before handoff, not a stand-in for Adobe Acrobat Preflight or a human prepress review.
Use Cases
- Pre-handoff check: verify bleed and font embedding within 30 seconds of exporting, instead of hearing about it from the printer tomorrow
- Incoming file triage: marketing runs outsourced artwork through once before forwarding to the printer, cutting the back-and-forth in half
- Business card validation: a 9×5.4 cm card shows a TrimBox with 9.6×6 cm bleed (3 mm per side, fine), but one image on the back sits at 132 DPI and gets flagged as an error, so swap in a high-res version before sending
- Office-file rescue: a client's Word-exported PDF has no TrimBox, the tool raises a warning, and you ask for a proper layout-software export before it ever reaches the press
- Reprinting old files: dig up a three-year-old catalog PDF and check fonts and image resolution before deciding whether it can go straight back to press
- A brand sends artwork to an overseas contract printer and runs preflight locally first, packaging the bleed and font-embedding results as an attachment so the vendor can skip re-confirming specs before production
FAQ
- Is the file really not uploaded?
- Really. The engines (pdf-lib and pdf.js) run as JavaScript inside your browser, and the network panel in your dev tools shows no upload request. It also means checking speed depends on your machine, not your connection.
- Does passing the check mean the file is press-ready?
- No. The tool covers the most common rejection reasons — bleed, fonts, resolution — but overprint, color spaces and total ink coverage are out of scope. Keep your printer's human prepress review before production.
- Why does my file show 'no TrimBox'?
- PDFs exported from office software usually carry only a page size, no finished-size box. For print, export from layout software (InDesign, Illustrator) with a press-quality PDF preset, bleed and crop marks enabled.
- Why do fonts have to be embedded?
- Because the output machine may not own the fonts you used. Without embedding, the system substitutes, spacing drifts and glyphs vanish, often discovered only at the printer's RIP. Press presets embed everything by default, so an unembedded font usually signals a broken export path.
- How is effective DPI different from the DPI stored in the image?
- The stored DPI is metadata. Effective DPI is image pixels divided by the size the image actually occupies on the page; the larger you place it, the lower it gets, and that is what determines printed sharpness.
- Is there a file size or page limit?
- Yes. The beta analyzes the first 20 pages and the first 50 images per page, and files over 50 MB are unsupported. For long catalogs or books, check in sections or run a full pass in Acrobat Pro's Preflight.
Limitations & Disclaimer
- Beta/PoC: analyzes the first 20 pages and 50 images per page; files over 50 MB are unsupported
- Out of scope: overprint and transparency, original image color spaces, PDF/X compliance, stroke widths, total ink coverage
- Passing is not a press-ready guarantee, so keep a human prepress review before production
- Detection only; the tool never modifies your original file
Need a Professional Check
What the tools give you is a digital reference. Before a production run, having an industry consultant review your proofs, specs and files costs far less than reprinting a bad batch
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