Portable Document Format is the most popular file format used by many for web publishing. When documents have to be sent by email over internet, PDF is used since the space utilization of the file is very less. When large files containing scanned documents or files in other formats are converted to PDF, their size is considerably higher. Many users still use dial up connections to connect to the internet. Large files pose a practical difficulty in cases they are sent as an attachment to an email over internet. To make a PDF smaller becomes the top priority for developers.
PDF compression is the process by which a PDF is made smaller. There are two different types of compression. They are lossy and lossless methods. In lossy method, high levels of compression may be done but there will be loss of data from the original document. In lossless method, the data consistency is maintained and no loss of data occurs. However, lesser levels of compression may be achieved by this method. PDF compression converts the original document into encoded format. This encoded format is then received at the receivers end and it is decompressed to get the original document back.
A PDF is made smaller by removing redundancies present in the document. The redundancies are mainly caused by repeating parts, multiple spaces and unwanted data in the form of outlines. These must be eliminated by substituting the particular data with an encoded string, which helps to make a PDF smaller. The PDF is made smaller by using complex algorithms, which look for patterns in the data in the document. These patterns are then encoded and made smaller. There must be decompression algorithms at the receivers end to get the data of the original documents data. Making a PDF smaller in size will result in saving bandwidth and time. Certain software available on the web is dedicated to PDF compression. These softwares have varying degrees of data consistency and compression levels. They may be chosen according to the requirements of the user. The user may prefer data consistency or compression ratio based on the need for compression.