Why PDF Compression?
In order to understand PDF compression, we must first get a grasp on basic data compression. In the simplest possible terms, data compression refers to the reduction of the size of electronic data. Specifically, it means reducing the number of bits that data occupies. When applied to large files, data compression results in files that require less disk or server space, load quicker, and can be transferred more easily.
PDF files are often ideal candidates for compression since the purpose of PDF as a format in the first place is ease of sharing and reading. PDF (portable document format) is often the preferred format for document sharing and storage due to its universality. PDF files look the same regardless of the machine or operating system on which they are opened; all that is required is a free PDF reader such as Adobe Reader. However, PDFs can become inconveniently large when they contain a large amount of high resolution content such as images and videos, or even just a very large number of pages. Large PDF files sometimes exceed email attachment limits; load slowly, especially from web pages; take up a lot of storage space; and are generally difficult to work with. This, of course, is where PDF compression comes in. PDF compression software can make bulky PDF files easy to work with again, and save users many headaches.
PDF Compression Software
PDF compression software uses various algorithms to achieve compression. There are two major data compression algorithm categories: lossless and lossy. Lossless compression algorithms work by finding logical patterns in the data being compressed and abbreviating them in such a way that they will be able to be reconstructed instantly when the file is opened. When applied to PDF files, this method results in compression without any loss to fidelity. Lossy compression algorithms, on the other hand, are capable of achieving greater compression rates than lossless ones, but result in some loss of fidelity. This is because lossy algorithms work by eliminating inessential data from the file. With PDF files, this usually results in some noticeable fidelity loss, although some lossy algorithms attempt to only eliminate data that the user won't notice missing. This is called perceptibly lossless compression. The main advantage to lossy compression is that it can result in much greater compression than lossless compression. Choosing the appropriate type of compression algorithm for PDF compression jobs is essential in order to maximize compression while achieving the desired fidelity. Some commonly used lossless compression algorithms are CCITT, Flate, LZW, RLE and ZIP; lossy algorithms include JPG and JPG2000.
Choosing the Right PDF Compression Product
When shopping for PDF compression software, it is typically a good idea to seek a product that includes both lossy and lossless compression algorithms so that you can customize the type of compression used for a given document or batch of documents. For example, if you want to make a PDF as small as possible for emailing, you will want to be able to choose an appropriate lossy algorithm; if fidelity is important, the option to use lossless compression is desirable. Also, you should compare compression rates, as some software products are more effective than others. The ability to convert image files of other types to PDF for compression is often useful, as is an OCR option for making your compressed PDFs text-searchable.
PdfCompressor, CVISION Technologies' flagship PDF compression product, uses the new JBIG2 and JPEG2000 compression algorithms, and includes convert-to-PDF and OCR functionality.