Understanding the PDF File Format: Overview

To make our popular “Understanding the PDF File Format” series an even better reference to learn from, we have categorized our posts and created this index. If you really want to know what goes on inside PDF files, these articles will give you all the details!

This is part 1 of the index, which is aimed to give an overview of the format. In part 2, we talk a lot more about PDF bugs, gotchas and tips!

If you just want to view, print, extract or search PDF, convert to or extract text in PDF, or convert to or extract images in PDF with the minimum of fuss, we recommend visiting our page of ready to run examples built into our JPedal PDF library!

The PDF File Format:

This section contains in depth information regarding how content is actually stored in a PDF file – what you see when you open a PDF in a text editor.

Viewing PDF Objects
PDF Object Streams
Multiple Trailers on PDF Files
PDF Xref Tables Explained
Text Streams
How are images stored?
PDF Dictionary
Named Locations
Linearized PDF Files
Form XObjects
More articles…

Images in PDF:

Images – An Overview
3 Examples of unusual ways to use PDF Image Masks
3 Types of Image Mask
Advantages of JBIG2 compression in PDF explained
There are several version of each image inside your PDF file
More articles…

If you require PDF to Image Conversion or Image Extraction from PDF, you may be interested in our Java PDF Library.

Colors in PDF:

Color – An Overview
PDF Image Color Depth
Indexed Colorspaces
The Color White in PDF Files
ICCBased Colorspaces
YCCK Color Conversion in PDF Files
More articles…

Text in PDF:

PDF Text – An Overview
PDF Text Co-ordinates
Carriage returns, spaces and other gaps
More articles…

If you require PDF Text Extraction, PDF to Text Conversion or PDF Text search, you may be interested in our Java PDF Library.

Fonts in PDF:

PDF Fonts – An Overview
Introduction to PDF Font Technologies
Embedded CMAP Tables
What are CID Fonts?
Custom Font Encodings
Are there really 3 types of fonts in PDF files?
Standard Font Information
Glyph Names – What is in a name?
TrueType Font Hinting

More articles…

PDF Forms, Annotations & Interactive Elements:

Introduction to PDF Forms
Introduction to FDF Forms
Introduction to XFA Forms
Interactive Elements
Layers in PDFs
More articles…

PDF Security:

PDF Security (Passwords and Certificates)
PDF Password Protection
Protecting PDF Content
More articles…


What new PDF developers need to know
Learning about PDF
Text, Shapes and Images
OCR (Optical Character Recognition) PDF files
Bookmarks and Links
What is PDF Pagesize? CropBox, MediaBox, ArtBox, BleedBox, TrimBox?
PDF Format and Style Information
A quick guide to PDF for Java (and non-Java) developers
Why writing a PDF parser is such a challenging task (Part 234)
Searching PDF Files
How do PDF files manage limitless position accuracy of shapes & images?
More articles…

Make your own PDF file – Hello World:

One of our developers bravely set out to write the ‘Hello World’ tutorial of PDF files, creating a PDF file from scratch manually, in a text editor. Follow the series here:

Part 1: PDF Objects and Data Types
Part 2: Structure of a PDF file
Part 2.5: Create a non working PDF
Part 3: DIY Blank Page
Part 4: Hello World Pdf
Part 5: Path objects
Part 6: Graphics State

If you enjoyed this index, we have also have a second, longer index covering all the nitty gritty details and gotchas we have found from over 13 years of working with PDF!

Is there something that we haven’t covered? Leave us a comment and we will see what we can do!

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Leon is a Developer at IDRsolutions, focusing mainly on development of the PDF to HTML5/SVG converter. He was a speaker at JavaOne 2012, co-presenting a session titled 'Lessons Learned in Writing a PDF-to-JavaFX Converter for NetBeans'.

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Leon Atherton

About Leon Atherton

Leon is a Developer at IDRsolutions, focusing mainly on development of the PDF to HTML5/SVG converter. He was a speaker at JavaOne 2012, co-presenting a session titled 'Lessons Learned in Writing a PDF-to-JavaFX Converter for NetBeans'.

One thought on “Understanding the PDF File Format: Overview

  1. Alejandro

    Hello, JPedal team :)
    First of all, allow me to express my satisfaction for reading such simple and clear PDF knowledges background. This is really helpful for who just starts into the PDF world. Thank you for this great job.
    I found these posts while looking for a *real* way of doing some redacts. I thought I had everything when I found ‘pdfedit’ (with a combination of its ‘replaceText’, its ‘findText’, its ‘drawRect’ and its ‘flattener’ functionalities), but then the ugly truth came up: sometimes not all characters are available. I guess it’s embedded fonts fault, but I am not quite sure. Here is when I started to read your posts ;)
    The fact is, I guess I will be able to implement a functional redact feature if found the way to ensure my replacement char (the one I use to replace each char of the redacted phrase) is in fact available. I see two scenarios here:
    1- the char is available (and so, everybody is happy :P), or
    2- the char is not available, but I am able to insert it to the right (embedded?) font.
    Could you help me to accomplish this, please? Some hints could be appreciated.
    Thanks in advance.
    Best regards and keep this spirit!


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