Blog
How the editor and its engine work, how we measure them against the specifications, and how to edit a PDF on the computer or phone you have.
The editor, the engine and the standards
How we measure CSS conformance on the web-platform-tests
We changed the unit behind our conformance headline: a reftest counts as one test, a scripted file counts as its subtests. Both scales, same dataset., a 5-minute read
Our PDF engine is now written in Rust, and measured on the web-platform-tests
Why we rewrote our HTML-to-PDF engine in Rust: the benchmark and its method, web-platform-tests results by CSS area, and what a PDF/UA validator misses., a 16-minute read
PDF/UA-2 (ISO 14289-2): what changes, and how we verify it
PDF/UA-2 is written on PDF 2.0. Five changes from PDF/UA-1, how to check each, and what veraPDF does not check., a 9-minute read
The Matterhorn Protocol: 136 ways a PDF can fail PDF/UA
PDF/UA-1 checkers test the conditions of the Matterhorn Protocol: 31 checkpoints, 136 failure conditions, and the split between machine checks and human judgement., a 3-minute read
Tagged and archival PDFs from ReflowPDF: the files, and how to check them
Exports that validate as PDF/UA-1, PDF/UA-2 and PDF/A-3a in veraPDF, each with its report. What the tags are, what the archive adds, and what no validator can judge for you., a 5-minute read
Why a PDF does not reflow, and how ReflowPDF edits one anyway
A PDF stores each line at a fixed place on a fixed page, so editors rewrap text only inside its box. ReflowPDF edits the document behind the pages., a 3-minute read
Guides
How to edit a PDF on an iPhone: what is built in, and what takes an editor
An iPhone signs, annotates and fills PDFs out of the box, but cannot change the text already in them. What each built-in tool does, and how to change the text in the browser., a 2-minute read
How to edit a PDF on a Mac: what Preview does, and where it stops
Preview signs, annotates, fills forms and rearranges pages, free and on the Mac. It cannot change the text already in a PDF. What it does, step by step, and how to change the text., a 2-minute read
How to edit a PDF on Android without paying for an app
Android has no built-in PDF editor. Google Drive and Acrobat Reader fill, sign and comment for free; changing the text takes an editor, which runs in Chrome., a 2-minute read
How to edit a PDF without Adobe Acrobat: which tool for which job
Signing, filling and annotating are built into Mac, iPhone, Chromebook and Windows; changing what a PDF says takes an editor. A job-by-job map., a 3-minute read
How to edit a table in a PDF without breaking the layout
In a PDF a table is text placed between drawn lines, so a new row means moving everything by hand. Rebuilt as a document, the table takes the row., a 2-minute read
