Most of the time, you can just use a PDF file without thinking about what lies ‘under the bonnet’. But sometimes you want to find out about the actual objects inside a PDF file.
I need to do this quite often to debug JPedal (Java PDF viewer and PDF to Image converter) and BuildVu (PDF to HTML5/SVG converter). It is very useful if you want to know about the colours used and how the PDF might print or whether it has any useful text. It also allows you to see how big the images inside the PDF really are and whether they can be easily extracted.
I used to open the PDF in a text editor but this is not an ideal solution. Not only can it be quite hard to decipher, but if the PDF is encrypted or contains compressed data and objects you cannot view these.
So I was really pleased to find a little feature hidden inside the Advanced menu option of Acrobat 9.0 to ‘Browse Internal PDF Structure‘
This allows you to see the actual PDF objects much more clearly. You will still need your trusty and well-thumbed copy of the Adobe Acrobat PDF specification but it has saved me a lot of time when needing to see what is happening inside a PDF file.
This post is part of our “Understanding the PDF File Format” series. In each article, we aim to take a specific PDF feature and explain it in simple terms. If you wish to learn more about PDF, we have 21 years worth of PDF knowledge and tips, so click here to visit our series index!
IDRsolutions develop a Java PDF library, a PDF forms to HTML5 converter, a PDF to HTML5 or SVG converter and a Java Image Library that doubles as an ImageIO replacement. On the blog our team post about anything interesting they learn about.