CCITT is a form of compression used in PDF files to squeeze down black and white data. This makes the PDF smaller (so faster to load and send). When the PDF page is decoded, the data is decompressed and converted back into the black and white image.
We have been doing some work on improving our CCITT decoder, so it seemed like a good item to write a series of articles about. You can read all the published articles in the series by clicking here. If you sign up for our RSS feed, you will be able to see the articles as they appear.
If you have any questions about CCITT compression (or any other aspect of PDF files), do let us know and we will try to add it into our blog articles.