Portable Document Format (PDF) is a file format used to present documents in a manner independent of application software, hardware, and operating systems.

PDF File Format

What does the ActualText dictionary tag do?

Text is defined in the PDF file format as a display value (normally what you see onscreen) and an extraction value. It is useful...
Mark Stephens
29 sec read

What are PDF Xref tables?

TL;DR: A PDF Xref table is an internal “map” of byte offsets that tells a reader exactly where to find specific objects (like fonts...
Mark Stephens
3 min read

What are Form XObjects?

Introduction Form XObjects (not be confused with forms which are buttons, checkboxes, buttons, etc) are an advanced feature of the PDF file format. They...
Mark Stephens
1 min read

Why is white a special color in PDF files?

White is a special color in the PDF file format. This is because of the way different colours work in the PDF file format....
Mark Stephens
1 min read

Why can’t I just open and edit a PDF…

People sometimes try to edit a PDF file by opening the file in a text editor. This very rarely works for 3 reasons. Firstly,...
Mark Stephens
1 min read

What does an OCR PDF file contain?

What is an OCR PDF file? Some PDF files are generated from scanning in pages as images, and these have their own unique quirks....
Mark Stephens
1 min read