If you know at least a bit about the PDF document format, you know that they can contain more than just text.
The obvious additions are, of course, graphics in the form of images, tables or charts. But text links, bookmarks, and even so-called “rich media” like sounds and videos can also be embedded in a PDF.
What is not as immediately obvious, is the structure and logic that is sometimes also part of the PDF. It’s present in so-called tagged PDFs and that’s what this article is all about.
What Is A Tagged PDF?
When talking about PDF, the “structure” refers to a set of rules or instructions inside that PDF that binds certain parts of its content. This includes a particular reading order or which graphic, form, table or list belongs to which paragraph of text.
This structure is expressed using tags within the document. With Adobe’s Acrobat Professional 6.0, automatic tagging was introduced. While tags are thus automatically added to PDF files, only the simplest documents deliver good results.
Advantages Of Properly Tagged PDFs
There are a couple of advantages of a properly tagged PDF. Thus, if you want to optimize your PDFs for a wider variety of people, consider manual tagging.
This process, however, is not an easy one. The slightest error in manual tagging could render the document in question as completely useless. Thus, there are some characteristics a properly tagged PDF should have and that should be considered when adding tags.
- Make sure that the tagged PDF includes a logical reading order for the text
- The Text inside the PDF should be in Unicode to eliminate irregularities
- Images should, just like on the web, have a correct alternative description
- Tables need proper tagging to correctly display the table structure
1. Tagged PDFs Can Reflow
If you are using a handheld device like a smartphone, or any kind of e-book reader, you can also open PDF documents. PDF is known for its rigid formatting that looks the same no matter which device or software you are using.
Especially on devices with a small screen, this means that you have to scroll inside the document in order to read. A tagged PDF, where paragraphs are bound in a “flowing” way, this scrolling is not necessary as the text flows depending on the width of your handheld screen.
2. Tagged PDFs Are Screen-Reader-Friendly
Visually impaired and blind people often use a screen-reader to navigate the internet and their files. A tagged PDF works better with such devices and software as it gives them more clues as what to tell their user. Thus, tags make a PDF more accessible and inclusive for visually disabled people.