Guides & tips for working with PDFs
Practical how-tos, behind-the-scenes notes, and product updates from the team behind Blackpdf.
Concepts & standards
Explainers on PDF versions, PDF/A, accessibility, and the ecosystem.
Concepts & standards
Explainers on PDF versions, PDF/A, accessibility, and the ecosystem.
How to Repair a Corrupted PDF
Fix a PDF that won't open, shows errors, or displays blank pages. Step-by-step guide for diagnosing damage and recovering as much as possible.
How to Compare Two PDFs and Spot the Differences
Compare two versions of a PDF side by side, as an overlay, or as a highlighted difference view. Step-by-step guide for catching changes between revisions.
How to Crop a PDF (Trim Margins or Adjust Pages)
Crop margins from a PDF or trim pages to a specific area. Step-by-step guide with auto-crop, precise margin values, and per-page versus whole-document crops.
PDF Accessibility Explained: Tagged PDFs and PDF/UA
Why some PDFs work with screen readers and others don't, what tagged PDFs are, how PDF/UA differs from PDF/A, and what makes a PDF legally accessible.
How to Resize PDF Pages to a Uniform Size
Fix a PDF with uneven page sizes. Resize pages to A4, Letter, Legal, or a custom size, choose how content scales, and normalize only the outliers.
Why a PDF's Pages End Up Different Sizes (and How Page Boxes Work)
A PDF stores a size on every page, not one for the whole file. Here's why pages drift apart, what MediaBox and CropBox actually do, and how to make them match.
PDF Versions Explained: What 1.4, 1.7, and 2.0 Actually Mean
Every PDF carries a version number in its header — 1.3, 1.4, 1.7, 2.0. Here's what each version adds, which one a system will accept, and when to change it.